chore: merge Jubilee to master

(cherry picked from commit 3f78f4d672)

.gitlab/CODEOWNERS

@@ -1 +1 @@
-* @go/bridge-ppl/devs
+* inbox-desktop-approvers

COPYING_NOTES.md

@@ -127,6 +127,7 @@ Proton Mail Bridge includes the following 3rd party software:
 * [blackfriday](https://github.com/russross/blackfriday/v2) available under [license](https://github.com/russross/blackfriday/v2/blob/master/LICENSE) 
 * [pflag](https://github.com/spf13/pflag) available under [license](https://github.com/spf13/pflag/blob/master/LICENSE) 
 * [bom](https://github.com/ssor/bom) available under [license](https://github.com/ssor/bom/blob/master/LICENSE) 
+* [objx](https://github.com/stretchr/objx) available under [license](https://github.com/stretchr/objx/blob/master/LICENSE) 
 * [golang-asm](https://github.com/twitchyliquid64/golang-asm) available under [license](https://github.com/twitchyliquid64/golang-asm/blob/master/LICENSE) 
 * [codec](https://github.com/ugorji/go/codec) available under [license](https://github.com/ugorji/go/codec/blob/master/LICENSE) 
 * [tagparser](https://github.com/vmihailenco/tagparser/v2) available under [license](https://github.com/vmihailenco/tagparser/v2/blob/master/LICENSE) 
@@ -141,6 +142,7 @@ Proton Mail Bridge includes the following 3rd party software:
 * [appengine](https://google.golang.org/appengine) available under [license](https://pkg.go.dev/google.golang.org/appengine?tab=licenses) 
 * [genproto](https://google.golang.org/genproto) available under [license](https://pkg.go.dev/google.golang.org/genproto?tab=licenses) 
 * [yaml](https://gopkg.in/yaml.v3) available under [license](https://github.com/go-yaml/yaml/blob/v3.0.1/LICENSE)  available under [license](https://github.com/go-yaml/yaml/blob/v3.0.1/LICENSE) 
+* [go-autostart](https://github.com/ElectroNafta/go-autostart) available under [license](https://github.com/ElectroNafta/go-autostart/blob/master/LICENSE) 
 * [go-message](https://github.com/ProtonMail/go-message) available under [license](https://github.com/ProtonMail/go-message/blob/master/LICENSE) 
 * [go-smtp](https://github.com/ProtonMail/go-smtp) available under [license](https://github.com/ProtonMail/go-smtp/blob/master/LICENSE) 
 * [resty](https://github.com/LBeernaertProton/resty/v2) available under [license](https://github.com/LBeernaertProton/resty/v2/blob/master/LICENSE) 

Changelog.md

@@ -3,6 +3,33 @@
 Changelog [format](http://keepachangelog.com/en/1.0.0/)
 
 
+## Jubilee Bridge 3.20.1
+
+### Fixed
+* BRIDGE-362: Implemented logic for reconciling label conflicts.
+
+
+## Jubilee Bridge 3.20.0
+
+### Added
+* BRIDGE-348: Enable display of BYOE addresses in Bridge.
+* BRIDGE-340: Added additional logging for label operations and related bad events.
+* BRIDGE-324: Log a hash of the vault key on Bridge start.
+
+### Changed
+* BRIDGE-352: Chore: bump go to 1.24.2.
+* BRIDGE-353: Chore: update x/net package to 0.38.0.
+
+### Fixed
+* BRIDGE-351: Allow draft creation and import to BYOE addresses in combined mode.
+* BRIDGE-301: Prevent imports into non-BYOE external addresses.
+* BRIDGE-341: Replaced go-autostart with a fork to support creating autostart shortcuts in directories with Unicode characters on Windows.
+* BRIDGE-332: Strip newline characters from username and password fields in the Bridge GUI.
+* BRIDGE-336: Ensure all remote labels are verified and created in Gluon at Bridge startup.
+* BRIDGE-335: Persist the last successfully used keychain helper as a user preference on Linux.
+* BRIDGE-333: Ignore unknown label IDs during Bridge synchronization.
+
+
 ## Infinity Bridge 3.19.0
 
 ### Changed

Makefile

@@ -12,7 +12,7 @@ ROOT_DIR:=$(realpath .)
 .PHONY: build build-gui build-nogui build-launcher versioner hasher
 
 # Keep version hardcoded so app build works also without Git repository.
-BRIDGE_APP_VERSION?=3.19.0+git
+BRIDGE_APP_VERSION?=3.20.1+git
 APP_VERSION:=${BRIDGE_APP_VERSION}
 APP_FULL_NAME:=Proton Mail Bridge
 APP_VENDOR:=Proton AG

go.mod

@@ -2,14 +2,14 @@ module github.com/ProtonMail/proton-bridge/v3
 
 go 1.24
 
-toolchain go1.24.0
+toolchain go1.24.2
 
 require (
 	github.com/0xAX/notificator v0.0.0-20220220101646-ee9b8921e557
 	github.com/Masterminds/semver/v3 v3.2.0
-	github.com/ProtonMail/gluon v0.17.1-0.20250116113909-2ebd96ec0bc2
+	github.com/ProtonMail/gluon v0.17.1-0.20250527153202-a7383713882a
 	github.com/ProtonMail/go-autostart v0.0.0-20210130080809-00ed301c8e9a
-	github.com/ProtonMail/go-proton-api v0.4.1-0.20250217140732-2e531f21de4c
+	github.com/ProtonMail/go-proton-api v0.4.1-0.20250417134000-e624a080f7ba
 	github.com/ProtonMail/gopenpgp/v2 v2.8.2-proton
 	github.com/PuerkitoBio/goquery v1.8.1
 	github.com/abiosoft/ishell v2.0.0+incompatible
@@ -46,10 +46,10 @@ require (
 	github.com/vmihailenco/msgpack/v5 v5.3.5
 	go.uber.org/goleak v1.2.1
 	golang.org/x/exp v0.0.0-20230522175609-2e198f4a06a1
-	golang.org/x/net v0.34.0
+	golang.org/x/net v0.38.0
 	golang.org/x/oauth2 v0.7.0
-	golang.org/x/sys v0.29.0
-	golang.org/x/text v0.21.0
+	golang.org/x/sys v0.31.0
+	golang.org/x/text v0.23.0
 	google.golang.org/api v0.114.0
 	google.golang.org/grpc v1.56.3
 	google.golang.org/protobuf v1.33.0
@@ -114,6 +114,7 @@ require (
 	github.com/russross/blackfriday/v2 v2.1.0 // indirect
 	github.com/spf13/pflag v1.0.5 // indirect
 	github.com/ssor/bom v0.0.0-20170718123548-6386211fdfcf // indirect
+	github.com/stretchr/objx v0.5.0 // indirect
 	github.com/twitchyliquid64/golang-asm v0.15.1 // indirect
 	github.com/ugorji/go/codec v1.2.11 // indirect
 	github.com/vmihailenco/tagparser/v2 v2.0.0 // indirect
@@ -121,9 +122,9 @@ require (
 	gitlab.com/c0b/go-ordered-json v0.0.0-20201030195603-febf46534d5a // indirect
 	go.opencensus.io v0.24.0 // indirect
 	golang.org/x/arch v0.3.0 // indirect
-	golang.org/x/crypto v0.32.0 // indirect
+	golang.org/x/crypto v0.36.0 // indirect
 	golang.org/x/mod v0.17.0 // indirect
-	golang.org/x/sync v0.10.0 // indirect
+	golang.org/x/sync v0.12.0 // indirect
 	golang.org/x/tools v0.21.1-0.20240508182429-e35e4ccd0d2d // indirect
 	google.golang.org/appengine v1.6.7 // indirect
 	google.golang.org/genproto v0.0.0-20230410155749-daa745c078e1 // indirect
@@ -131,6 +132,7 @@ require (
 )
 
 replace (
+	github.com/ProtonMail/go-autostart => github.com/ElectroNafta/go-autostart v0.0.0-20250402094843-326608c16033
 	github.com/emersion/go-message => github.com/ProtonMail/go-message v0.13.1-0.20240919135104-3bc88e6a9423
 	github.com/emersion/go-smtp => github.com/ProtonMail/go-smtp v0.0.0-20231109081432-2b3d50599865
 	github.com/go-resty/resty/v2 => github.com/LBeernaertProton/resty/v2 v2.0.0-20231129100320-dddf8030d93a

go.sum

@@ -23,6 +23,8 @@ github.com/0xAX/notificator v0.0.0-20220220101646-ee9b8921e557 h1:l6surSnJ3RP4qA
 github.com/0xAX/notificator v0.0.0-20220220101646-ee9b8921e557/go.mod h1:sTrmvD/TxuypdOERsDOS7SndZg0rzzcCi1b6wQMXUYM=
 github.com/BurntSushi/toml v0.3.1/go.mod h1:xHWCNGjB5oqiDr8zfno3MHue2Ht5sIBksp03qcyfWMU=
 github.com/BurntSushi/xgb v0.0.0-20160522181843-27f122750802/go.mod h1:IVnqGOEym/WlBOVXweHU+Q+/VP0lqqI8lqeDx9IjBqo=
+github.com/ElectroNafta/go-autostart v0.0.0-20250402094843-326608c16033 h1:d2RB9rQmSusb0K+qSgB+DAY+8i+AXZ/o+oDHj2vAUaA=
+github.com/ElectroNafta/go-autostart v0.0.0-20250402094843-326608c16033/go.mod h1:o0nKiWcK0e2G/90uL6akWRkzOV4mFcZmvpBPpigJvdw=
 github.com/Kodeworks/golang-image-ico v0.0.0-20141118225523-73f0f4cfade9/go.mod h1:7uhhqiBaR4CpN0k9rMjOtjpcfGd6DG2m04zQxKnWQ0I=
 github.com/LBeernaertProton/resty/v2 v2.0.0-20231129100320-dddf8030d93a h1:eQO/GF/+H8/9udc9QAgieFr+jr1tjXlJo35RAhsUbWY=
 github.com/LBeernaertProton/resty/v2 v2.0.0-20231129100320-dddf8030d93a/go.mod h1:iiP/OpA0CkcL3IGt1O0+/SIItFUbkkyw5BGXiVdTu+A=
@@ -34,10 +36,10 @@ github.com/OneOfOne/xxhash v1.2.2/go.mod h1:HSdplMjZKSmBqAxg5vPj2TmRDmfkzw+cTzAE
 github.com/ProtonMail/bcrypt v0.0.0-20210511135022-227b4adcab57/go.mod h1:HecWFHognK8GfRDGnFQbW/LiV7A3MX3gZVs45vk5h8I=
 github.com/ProtonMail/bcrypt v0.0.0-20211005172633-e235017c1baf h1:yc9daCCYUefEs69zUkSzubzjBbL+cmOXgnmt9Fyd9ug=
 github.com/ProtonMail/bcrypt v0.0.0-20211005172633-e235017c1baf/go.mod h1:o0ESU9p83twszAU8LBeJKFAAMX14tISa0yk4Oo5TOqo=
-github.com/ProtonMail/gluon v0.17.1-0.20250116113909-2ebd96ec0bc2 h1:lDgMidI/9j2eedavcy7YICv8+F73ooVTUoUGBE4dO0s=
-github.com/ProtonMail/gluon v0.17.1-0.20250116113909-2ebd96ec0bc2/go.mod h1:0/c03TzZPNiSgY5UDJK1iRDkjlDPwWugxTT6et2qDu8=
-github.com/ProtonMail/go-autostart v0.0.0-20210130080809-00ed301c8e9a h1:D+aZah+k14Gn6kmL7eKxoo/4Dr/lK3ChBcwce2+SQP4=
-github.com/ProtonMail/go-autostart v0.0.0-20210130080809-00ed301c8e9a/go.mod h1:oTGdE7/DlWIr23G0IKW3OXK9wZ5Hw1GGiaJFccTvZi4=
+github.com/ProtonMail/gluon v0.17.1-0.20250527093338-0b0a59c5f7d2 h1:BWo8ntIFkCeh6o2f2btbDQbUT0GYXuF5BNUOkaCbgws=
+github.com/ProtonMail/gluon v0.17.1-0.20250527093338-0b0a59c5f7d2/go.mod h1:0/c03TzZPNiSgY5UDJK1iRDkjlDPwWugxTT6et2qDu8=
+github.com/ProtonMail/gluon v0.17.1-0.20250527153202-a7383713882a h1:6OhwrrhJ7/agGXC0ulIqgfzuAs33ILUs61KW5AcHcH4=
+github.com/ProtonMail/gluon v0.17.1-0.20250527153202-a7383713882a/go.mod h1:0/c03TzZPNiSgY5UDJK1iRDkjlDPwWugxTT6et2qDu8=
 github.com/ProtonMail/go-crypto v0.0.0-20230321155629-9a39f2531310/go.mod h1:8TI4H3IbrackdNgv+92dI+rhpCaLqM0IfpgCgenFvRE=
 github.com/ProtonMail/go-crypto v1.1.4-proton h1:KIo9uNlk3vzlwI7o5VjhiEjI4Ld1TDixOMnoNZyfpFE=
 github.com/ProtonMail/go-crypto v1.1.4-proton/go.mod h1:zNoyBJW3p/yVWiHNZgfTF9VsjwqYof5YY0M9kt2QaX0=
@@ -45,10 +47,8 @@ github.com/ProtonMail/go-message v0.13.1-0.20240919135104-3bc88e6a9423 h1:p8nBDx
 github.com/ProtonMail/go-message v0.13.1-0.20240919135104-3bc88e6a9423/go.mod h1:NBAn21zgCJ/52WLDyed18YvYFm5tEoeDauubFqLokM4=
 github.com/ProtonMail/go-mime v0.0.0-20230322103455-7d82a3887f2f h1:tCbYj7/299ekTTXpdwKYF8eBlsYsDVoggDAuAjoK66k=
 github.com/ProtonMail/go-mime v0.0.0-20230322103455-7d82a3887f2f/go.mod h1:gcr0kNtGBqin9zDW9GOHcVntrwnjrK+qdJ06mWYBybw=
-github.com/ProtonMail/go-proton-api v0.4.1-0.20250121114701-67bd01ad0bc3 h1:YYnLBVcg7WrEbYVmF1PBr4AEQlob9rCphsMHAmF4CAo=
-github.com/ProtonMail/go-proton-api v0.4.1-0.20250121114701-67bd01ad0bc3/go.mod h1:RYgagBFkA3zFrSt7/vviFFwjZxBo6pGzcTwFsLwsnyc=
-github.com/ProtonMail/go-proton-api v0.4.1-0.20250217140732-2e531f21de4c h1:dxnbB+ov77BDj1LC35fKZ14hLoTpU6OTpZySwxarVx0=
-github.com/ProtonMail/go-proton-api v0.4.1-0.20250217140732-2e531f21de4c/go.mod h1:RYgagBFkA3zFrSt7/vviFFwjZxBo6pGzcTwFsLwsnyc=
+github.com/ProtonMail/go-proton-api v0.4.1-0.20250417134000-e624a080f7ba h1:DFBngZ7u/f69flRFzPp6Ipo6PKEyflJlA5OCh52yDB4=
+github.com/ProtonMail/go-proton-api v0.4.1-0.20250417134000-e624a080f7ba/go.mod h1:eXIoLyIHxvPo8Kd9e1ygYIrAwbeWJhLi3vgSz2crlK4=
 github.com/ProtonMail/go-smtp v0.0.0-20231109081432-2b3d50599865 h1:EP1gnxLL5Z7xBSymE9nSTM27nRYINuvssAtDmG0suD8=
 github.com/ProtonMail/go-smtp v0.0.0-20231109081432-2b3d50599865/go.mod h1:qm27SGYgoIPRot6ubfQ/GpiPy/g3PaZAVRxiO/sDUgQ=
 github.com/ProtonMail/go-srp v0.0.7 h1:Sos3Qk+th4tQR64vsxGIxYpN3rdnG9Wf9K4ZloC1JrI=
@@ -500,8 +500,8 @@ golang.org/x/crypto v0.0.0-20200622213623-75b288015ac9/go.mod h1:LzIPMQfyMNhhGPh
 golang.org/x/crypto v0.0.0-20210921155107-089bfa567519/go.mod h1:GvvjBRRGRdwPK5ydBHafDWAxML/pGHZbMvKqRZ5+Abc=
 golang.org/x/crypto v0.7.0/go.mod h1:pYwdfH91IfpZVANVyUOhSIPZaFoJGxTFbZhFTx+dXZU=
 golang.org/x/crypto v0.14.0/go.mod h1:MVFd36DqK4CsrnJYDkBA3VC4m2GkXAM0PvzMCn4JQf4=
-golang.org/x/crypto v0.32.0 h1:euUpcYgM8WcP71gNpTqQCn6rC2t6ULUPiOzfWaXVVfc=
-golang.org/x/crypto v0.32.0/go.mod h1:ZnnJkOaASj8g0AjIduWNlq2NRxL0PlBrbKVyZ6V/Ugc=
+golang.org/x/crypto v0.36.0 h1:AnAEvhDddvBdpY+uR+MyHmuZzzNqXSe/GvuDeob5L34=
+golang.org/x/crypto v0.36.0/go.mod h1:Y4J0ReaxCR1IMaabaSMugxJES1EpwhBHhv2bDHklZvc=
 golang.org/x/exp v0.0.0-20190121172915-509febef88a4/go.mod h1:CJ0aWSM057203Lf6IL+f9T1iT9GByDxfZKAQTCR3kQA=
 golang.org/x/exp v0.0.0-20190306152737-a1d7652674e8/go.mod h1:CJ0aWSM057203Lf6IL+f9T1iT9GByDxfZKAQTCR3kQA=
 golang.org/x/exp v0.0.0-20190510132918-efd6b22b2522/go.mod h1:ZjyILWgesfNpC6sMxTJOJm9Kp84zZh5NQWvqDGG3Qr8=
@@ -557,8 +557,8 @@ golang.org/x/net v0.8.0/go.mod h1:QVkue5JL9kW//ek3r6jTKnTFis1tRmNAW2P1shuFdJc=
 golang.org/x/net v0.9.0/go.mod h1:d48xBJpPfHeWQsugry2m+kC02ZBRGRgulfHnEXEuWns=
 golang.org/x/net v0.10.0/go.mod h1:0qNGK6F8kojg2nk9dLZ2mShWaEBan6FAoqfSigmmuDg=
 golang.org/x/net v0.17.0/go.mod h1:NxSsAGuq816PNPmqtQdLE42eU2Fs7NoRIZrHJAlaCOE=
-golang.org/x/net v0.34.0 h1:Mb7Mrk043xzHgnRM88suvJFwzVrRfHEHJEl5/71CKw0=
-golang.org/x/net v0.34.0/go.mod h1:di0qlW3YNM5oh6GqDGQr92MyTozJPmybPK4Ev/Gm31k=
+golang.org/x/net v0.38.0 h1:vRMAPTMaeGqVhG5QyLJHqNDwecKTomGeqbnfZyKlBI8=
+golang.org/x/net v0.38.0/go.mod h1:ivrbrMbzFq5J41QOQh0siUuly180yBYtLp+CKbEaFx8=
 golang.org/x/oauth2 v0.0.0-20180821212333-d2e6202438be/go.mod h1:N/0e6XlmueqKjAGxoOufVs8QHGRruUQn6yWY3a++T0U=
 golang.org/x/oauth2 v0.0.0-20190226205417-e64efc72b421/go.mod h1:gOpvHmFTYa4IltrdGE7lF6nIHvwfUNPOp7c8zoXwtLw=
 golang.org/x/oauth2 v0.0.0-20190604053449-0f29369cfe45/go.mod h1:gOpvHmFTYa4IltrdGE7lF6nIHvwfUNPOp7c8zoXwtLw=
@@ -573,8 +573,8 @@ golang.org/x/sync v0.0.0-20190911185100-cd5d95a43a6e/go.mod h1:RxMgew5VJxzue5/jJ
 golang.org/x/sync v0.0.0-20210220032951-036812b2e83c/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.0.0-20220722155255-886fb9371eb4/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.1.0/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
-golang.org/x/sync v0.10.0 h1:3NQrjDixjgGwUOCaF8w2+VYHv0Ve/vGYSbdkTa98gmQ=
-golang.org/x/sync v0.10.0/go.mod h1:Czt+wKu1gCyEFDUtn0jG5QVvpJ6rzVqr5aXyt9drQfk=
+golang.org/x/sync v0.12.0 h1:MHc5BpPuC30uJk597Ri8TV3CNZcTLu6B6z4lJy+g6Jw=
+golang.org/x/sync v0.12.0/go.mod h1:1dzgHSNfp02xaA81J2MS99Qcpr2w7fw1gpm99rleRqA=
 golang.org/x/sys v0.0.0-20180823144017-11551d06cbcc/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20180830151530-49385e6e1522/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20180905080454-ebe1bf3edb33/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
@@ -613,8 +613,8 @@ golang.org/x/sys v0.6.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.7.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.8.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.13.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/sys v0.29.0 h1:TPYlXGxvx1MGTn2GiZDhnjPA9wZzZeGKHHmKhHYvgaU=
-golang.org/x/sys v0.29.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
+golang.org/x/sys v0.31.0 h1:ioabZlmFYtWhL+TRYpcnNlLwhyxaM9kWTDEmfnprqik=
+golang.org/x/sys v0.31.0/go.mod h1:BJP2sWEmIv4KK5OTEluFJCKSidICx8ciO85XgH3Ak8k=
 golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=
 golang.org/x/term v0.0.0-20210927222741-03fcf44c2211/go.mod h1:jbD1KX2456YbFQfuXm/mYQcufACuNUgVhRMnK/tPxf8=
 golang.org/x/term v0.5.0/go.mod h1:jMB1sMXY+tzblOD4FWmEbocvup2/aLOaQEp7JmGp78k=
@@ -634,8 +634,8 @@ golang.org/x/text v0.7.0/go.mod h1:mrYo+phRRbMaCq/xk9113O4dZlRixOauAjOtrjsXDZ8=
 golang.org/x/text v0.8.0/go.mod h1:e1OnstbJyHTd6l/uOt8jFFHp6TRDWZR/bV3emEE/zU8=
 golang.org/x/text v0.9.0/go.mod h1:e1OnstbJyHTd6l/uOt8jFFHp6TRDWZR/bV3emEE/zU8=
 golang.org/x/text v0.13.0/go.mod h1:TvPlkZtksWOMsz7fbANvkp4WM8x/WCo/om8BMLbz+aE=
-golang.org/x/text v0.21.0 h1:zyQAAkrwaneQ066sspRyJaG9VNi/YJ1NfzcGB3hZ/qo=
-golang.org/x/text v0.21.0/go.mod h1:4IBbMaMmOPCJ8SecivzSH54+73PCFmPWxNTLm+vZkEQ=
+golang.org/x/text v0.23.0 h1:D71I7dUrlY+VX0gQShAThNGHFxZ13dGLBHQLVl1mJlY=
+golang.org/x/text v0.23.0/go.mod h1:/BLNzu4aZCJ1+kcD0DNRotWKage4q2rGVAg4o22unh4=
 golang.org/x/time v0.0.0-20181108054448-85acf8d2951c/go.mod h1:tRJNPiyCQ0inRvYxbN9jk5I+vvW/OXSQhTDSoE431IQ=
 golang.org/x/time v0.0.0-20190308202827-9d24e82272b4/go.mod h1:tRJNPiyCQ0inRvYxbN9jk5I+vvW/OXSQhTDSoE431IQ=
 golang.org/x/time v0.3.0 h1:rg5rLMjNzMS1RkNLzCG38eapWhnYLFYXDXj2gOlr8j4=

internal/app/migration.go

@@ -138,7 +138,7 @@ func migrateOldAccounts(locations *locations.Locations, keychains *keychain.List
 	if err != nil {
 		return fmt.Errorf("failed to get helper: %w", err)
 	}
-	keychain, err := keychain.NewKeychain(helper, "bridge", keychains.GetHelpers(), keychains.GetDefaultHelper())
+	keychain, _, err := keychain.NewKeychain(helper, "bridge", keychains.GetHelpers(), keychains.GetDefaultHelper())
 	if err != nil {
 		return fmt.Errorf("failed to create keychain: %w", err)
 	}

internal/app/migration_test.go

@@ -134,7 +134,7 @@ func TestKeychainMigration(t *testing.T) {
 func TestUserMigration(t *testing.T) {
 	kcl := keychain.NewTestKeychainsList()
 
-	kc, err := keychain.NewKeychain("mock", "bridge", kcl.GetHelpers(), kcl.GetDefaultHelper())
+	kc, _, err := keychain.NewKeychain("mock", "bridge", kcl.GetHelpers(), kcl.GetDefaultHelper())
 	require.NoError(t, err)
 
 	require.NoError(t, kc.Put("brokenID", "broken"))

internal/app/vault.go

@@ -18,6 +18,8 @@
 package app
 
 import (
+	"crypto/sha256"
+	"encoding/hex"
 	"fmt"
 	"path"
 
@@ -67,11 +69,12 @@ func newVault(reporter *sentry.Reporter, locations *locations.Locations, keychai
 	logrus.WithField("vaultDir", vaultDir).Debug("Loading vault from directory")
 
 	var (
-		vaultKey []byte
-		insecure bool
+		vaultKey       []byte
+		insecure       bool
+		lastUsedHelper string
 	)
 
-	if key, err := loadVaultKey(vaultDir, keychains); err != nil {
+	if key, helper, err := loadVaultKey(vaultDir, keychains); err != nil {
 		if reporter != nil {
 			if rerr := reporter.ReportMessageWithContext("Could not load/create vault key", map[string]any{
 				"keychainDefaultHelper":       keychains.GetDefaultHelper(),
@@ -89,6 +92,8 @@ func newVault(reporter *sentry.Reporter, locations *locations.Locations, keychai
 		vaultDir = path.Join(vaultDir, "insecure")
 	} else {
 		vaultKey = key
+		lastUsedHelper = helper
+		logHashedVaultKey(vaultKey) // Log a hash of the vault key.
 	}
 
 	gluonCacheDir, err := locations.ProvideGluonCachePath()
@@ -96,34 +101,47 @@ func newVault(reporter *sentry.Reporter, locations *locations.Locations, keychai
 		return nil, false, nil, fmt.Errorf("could not provide gluon path: %w", err)
 	}
 
-	vault, corrupt, err := vault.New(vaultDir, gluonCacheDir, vaultKey, panicHandler)
+	userVault, corrupt, err := vault.New(vaultDir, gluonCacheDir, vaultKey, panicHandler)
 	if err != nil {
 		return nil, false, corrupt, fmt.Errorf("could not create vault: %w", err)
 	}
 
-	return vault, insecure, corrupt, nil
+	// Remember the last successfully used keychain and store that as the user preference.
+	if err := vault.SetHelper(vaultDir, lastUsedHelper); err != nil {
+		logrus.WithError(err).Error("Could not store last used keychain helper")
+	}
+
+	return userVault, insecure, corrupt, nil
 }
 
-func loadVaultKey(vaultDir string, keychains *keychain.List) ([]byte, error) {
-	helper, err := vault.GetHelper(vaultDir)
+// loadVaultKey - loads the key used to encrypt the vault alongside the keychain helper used to access it.
+func loadVaultKey(vaultDir string, keychains *keychain.List) (key []byte, keychainHelper string, err error) {
+	keychainHelper, err = vault.GetHelper(vaultDir)
 	if err != nil {
-		return nil, fmt.Errorf("could not get keychain helper: %w", err)
+		return nil, keychainHelper, fmt.Errorf("could not get keychain helper: %w", err)
 	}
 
-	kc, err := keychain.NewKeychain(helper, constants.KeyChainName, keychains.GetHelpers(), keychains.GetDefaultHelper())
+	kc, keychainHelper, err := keychain.NewKeychain(keychainHelper, constants.KeyChainName, keychains.GetHelpers(), keychains.GetDefaultHelper())
 	if err != nil {
-		return nil, fmt.Errorf("could not create keychain: %w", err)
+		return nil, keychainHelper, fmt.Errorf("could not create keychain: %w", err)
 	}
 
-	key, err := vault.GetVaultKey(kc)
+	key, err = vault.GetVaultKey(kc)
 	if err != nil {
 		if keychain.IsErrKeychainNoItem(err) {
 			logrus.WithError(err).Warn("no vault key found, generating new")
-			return vault.NewVaultKey(kc)
+			key, err := vault.NewVaultKey(kc)
+			return key, keychainHelper, err
 		}
 
-		return nil, fmt.Errorf("could not check for vault key: %w", err)
+		return nil, keychainHelper, fmt.Errorf("could not check for vault key: %w", err)
 	}
 
-	return key, nil
+	return key, keychainHelper, nil
+}
+
+// logHashedVaultKey - computes a sha256 hash and encodes it to base 64. The resulting string is logged.
+func logHashedVaultKey(vaultKey []byte) {
+	hashedKey := sha256.Sum256(vaultKey)
+	logrus.WithField("hashedKey", hex.EncodeToString(hashedKey[:])).Info("Found vault key")
 }

internal/bridge/bridge_test.go

@@ -618,7 +618,7 @@ func TestBridge_AddressWithoutKeys(t *testing.T) {
 			require.NoError(t, err)
 
 			// Create an additional address for the user; it will not have keys.
-			aliasAddrID, err := s.CreateAddress(userID, "alias@pm.me", []byte("password"))
+			aliasAddrID, err := s.CreateAddress(userID, "alias@pm.me", []byte("password"), true)
 			require.NoError(t, err)
 
 			// Create an API client so we can remove the address keys.
@@ -785,7 +785,7 @@ func TestBridge_ChangeAddressOrder(t *testing.T) {
 		require.NoError(t, err)
 
 		// Create a second address for the user.
-		aliasID, err := s.CreateAddress(userID, "alias@"+s.GetDomain(), password)
+		aliasID, err := s.CreateAddress(userID, "alias@"+s.GetDomain(), password, true)
 		require.NoError(t, err)
 
 		// Create 10 messages for the user.

internal/bridge/observability_test.go

@@ -127,9 +127,9 @@ func TestBridge_Observability_UserMetric(t *testing.T) {
 	}
 
 	withEnv(t, func(ctx context.Context, s *server.Server, netCtl *proton.NetCtl, locator bridge.Locator, vaultKey []byte) {
-		userMetricPeriod := time.Millisecond * 200
+		userMetricPeriod := time.Millisecond * 600
 		heartbeatPeriod := time.Second * 10
-		throttlePeriod := time.Millisecond * 100
+		throttlePeriod := time.Millisecond * 300
 		observability.ModifyUserMetricInterval(userMetricPeriod)
 		observability.ModifyThrottlePeriod(throttlePeriod)
 

internal/bridge/sync_test.go

@@ -355,7 +355,7 @@ func TestBridge_CanProcessEventsDuringSync(t *testing.T) {
 
 			// Create a new address
 			newAddress := "foo@proton.ch"
-			addrID, err := s.CreateAddress(userID, newAddress, password)
+			addrID, err := s.CreateAddress(userID, newAddress, password, true)
 			require.NoError(t, err)
 
 			event := <-addressCreatedCh
@@ -430,7 +430,7 @@ func TestBridge_EventReplayAfterSyncHasFinished(t *testing.T) {
 			createNumMessages(ctx, t, c, addrID, labelID, numMsg)
 		})
 
-		addrID1, err := s.CreateAddress(userID, "foo@proton.ch", password)
+		addrID1, err := s.CreateAddress(userID, "foo@proton.ch", password, true)
 		require.NoError(t, err)
 
 		var allowSyncToProgress atomic.Bool
@@ -469,7 +469,7 @@ func TestBridge_EventReplayAfterSyncHasFinished(t *testing.T) {
 			})
 
 			// User AddrID2 event as a check point to see when the new address was created.
-			addrID2, err := s.CreateAddress(userID, "bar@proton.ch", password)
+			addrID2, err := s.CreateAddress(userID, "bar@proton.ch", password, true)
 			require.NoError(t, err)
 
 			allowSyncToProgress.Store(true)
@@ -552,7 +552,7 @@ func TestBridge_MessageCreateDuringSync(t *testing.T) {
 			})
 
 			// User AddrID2 event as a check point to see when the new address was created.
-			addrID, err := s.CreateAddress(userID, "bar@proton.ch", password)
+			addrID, err := s.CreateAddress(userID, "bar@proton.ch", password, true)
 			require.NoError(t, err)
 
 			// At most two events can be published, one for the first address, then for the second.
@@ -663,7 +663,7 @@ func TestBridge_AddressOrderChangeDuringSyncInCombinedModeDoesNotTriggerBadEvent
 			require.Equal(t, 1, len(info.Addresses))
 			require.Equal(t, info.Addresses[0], "user@proton.local")
 
-			addrID2, err := s.CreateAddress(userID, "foo@"+s.GetDomain(), password)
+			addrID2, err := s.CreateAddress(userID, "foo@"+s.GetDomain(), password, true)
 			require.NoError(t, err)
 
 			require.NoError(t, s.SetAddressOrder(userID, []string{addrID2, addrID}))

internal/bridge/user_event_test.go

@@ -304,7 +304,7 @@ func TestBridge_User_AddressEvents_NoBadEvent(t *testing.T) {
 		withBridge(ctx, t, s.GetHostURL(), netCtl, locator, storeKey, func(bridge *bridge.Bridge, _ *bridge.Mocks) {
 			userLoginAndSync(ctx, t, bridge, "user", password)
 
-			addrID, err = s.CreateAddress(userID, "other@pm.me", password)
+			addrID, err = s.CreateAddress(userID, "other@pm.me", password, true)
 			require.NoError(t, err)
 			userContinueEventProcess(ctx, t, s, bridge)
 
@@ -312,7 +312,7 @@ func TestBridge_User_AddressEvents_NoBadEvent(t *testing.T) {
 			userContinueEventProcess(ctx, t, s, bridge)
 		})
 
-		otherID, err := s.CreateAddress(userID, "another@pm.me", password)
+		otherID, err := s.CreateAddress(userID, "another@pm.me", password, true)
 		require.NoError(t, err)
 		require.NoError(t, s.RemoveAddress(userID, otherID))
 
@@ -328,6 +328,87 @@ func TestBridge_User_AddressEvents_NoBadEvent(t *testing.T) {
 	})
 }
 
+func TestBridge_User_AddressEvents_BYOEAddressAdded(t *testing.T) {
+	withEnv(t, func(ctx context.Context, s *server.Server, netCtl *proton.NetCtl, locator bridge.Locator, storeKey []byte) {
+		// Create a user.
+		userID, addrID, err := s.CreateUser("user", password)
+		require.NoError(t, err)
+
+		withBridge(ctx, t, s.GetHostURL(), netCtl, locator, storeKey, func(bridge *bridge.Bridge, _ *bridge.Mocks) {
+			userLoginAndSync(ctx, t, bridge, "user", password)
+
+			// Create an additional proton address
+			addrID, err = s.CreateAddress(userID, "other@pm.me", password, true)
+			require.NoError(t, err)
+			userContinueEventProcess(ctx, t, s, bridge)
+			require.NoError(t, s.AddAddressCreatedEvent(userID, addrID))
+			userContinueEventProcess(ctx, t, s, bridge)
+
+			userInfo, err := bridge.GetUserInfo(userID)
+			require.NoError(t, err)
+			require.Equal(t, 2, len(userInfo.Addresses))
+
+			// Create an external address with sending disabled.
+			externalID, err := s.CreateExternalAddress(userID, "another@yahoo.com", password, false)
+			require.NoError(t, err)
+			userContinueEventProcess(ctx, t, s, bridge)
+			require.NoError(t, s.AddAddressCreatedEvent(userID, externalID))
+			userContinueEventProcess(ctx, t, s, bridge)
+
+			// User addresses should still return 2, as we ignore the external address.
+			userInfo, err = bridge.GetUserInfo(userID)
+			require.NoError(t, err)
+			require.Equal(t, 2, len(userInfo.Addresses))
+
+			// Create an external address w. sending enabled. This is considered a BYOE address.
+			BYOEAddrID, err := s.CreateExternalAddress(userID, "other@yahoo.com", password, true)
+			require.NoError(t, err)
+			userContinueEventProcess(ctx, t, s, bridge)
+			require.NoError(t, s.AddAddressCreatedEvent(userID, BYOEAddrID))
+			userContinueEventProcess(ctx, t, s, bridge)
+
+			userInfo, err = bridge.GetUserInfo(userID)
+			require.NoError(t, err)
+			require.Equal(t, 3, len(userInfo.Addresses))
+		})
+	})
+}
+
+func TestBridge_User_AddressEvents_ExternalAddressSendChanged(t *testing.T) {
+	withEnv(t, func(ctx context.Context, s *server.Server, netCtl *proton.NetCtl, locator bridge.Locator, storeKey []byte) {
+		userID, _, err := s.CreateUser("user", password)
+		require.NoError(t, err)
+
+		withBridge(ctx, t, s.GetHostURL(), netCtl, locator, storeKey, func(bridge *bridge.Bridge, _ *bridge.Mocks) {
+			userLoginAndSync(ctx, t, bridge, "user", password)
+
+			// Create an additional external address.
+			externalID, err := s.CreateExternalAddress(userID, "other@yahoo.me", password, false)
+			require.NoError(t, err)
+			userContinueEventProcess(ctx, t, s, bridge)
+			require.NoError(t, s.AddAddressCreatedEvent(userID, externalID))
+			userContinueEventProcess(ctx, t, s, bridge)
+
+			// We expect only one address, the external one without sending should not be considered a valid address.
+			userInfo, err := bridge.GetUserInfo(userID)
+			require.NoError(t, err)
+			require.Equal(t, 1, len(userInfo.Addresses))
+
+			// Change it to allow sending such that it becomes a BYOE address.
+			err = s.ChangeAddressAllowSend(userID, externalID, true)
+			require.NoError(t, err)
+			userContinueEventProcess(ctx, t, s, bridge)
+			require.NoError(t, s.AddAddressUpdatedEvent(userID, externalID))
+			userContinueEventProcess(ctx, t, s, bridge)
+
+			// We should now have 2 usable addresses listed.
+			userInfo, err = bridge.GetUserInfo(userID)
+			require.NoError(t, err)
+			require.Equal(t, 2, len(userInfo.Addresses))
+		})
+	})
+}
+
 func TestBridge_User_AddressEventUpdatedForAddressThatDoesNotExist_NoBadEvent(t *testing.T) {
 	withEnv(t, func(ctx context.Context, s *server.Server, netCtl *proton.NetCtl, locator bridge.Locator, storeKey []byte) {
 		// Create a user.
@@ -694,7 +775,7 @@ func TestBridge_User_DisableEnableAddress(t *testing.T) {
 		require.NoError(t, err)
 
 		// Create an additional address for the user.
-		aliasID, err := s.CreateAddress(userID, "alias@"+s.GetDomain(), password)
+		aliasID, err := s.CreateAddress(userID, "alias@"+s.GetDomain(), password, true)
 		require.NoError(t, err)
 
 		withBridge(ctx, t, s.GetHostURL(), netCtl, locator, storeKey, func(bridge *bridge.Bridge, _ *bridge.Mocks) {
@@ -745,7 +826,7 @@ func TestBridge_User_CreateDisabledAddress(t *testing.T) {
 		require.NoError(t, err)
 
 		// Create an additional address for the user.
-		aliasID, err := s.CreateAddress(userID, "alias@"+s.GetDomain(), password)
+		aliasID, err := s.CreateAddress(userID, "alias@"+s.GetDomain(), password, true)
 		require.NoError(t, err)
 
 		// Immediately disable the address.

internal/bridge/user_test.go

@@ -658,7 +658,7 @@ func TestBridge_UserInfo_Alias(t *testing.T) {
 			require.NoError(t, err)
 
 			// Give the new user an alias.
-			require.NoError(t, getErr(s.CreateAddress(userID, "alias@pm.me", []byte("password"))))
+			require.NoError(t, getErr(s.CreateAddress(userID, "alias@pm.me", []byte("password"), true)))
 
 			// Login the user.
 			require.NoError(t, getErr(bridge.LoginFull(ctx, "primary", []byte("password"), nil, nil)))
@@ -706,7 +706,7 @@ func TestBridge_User_GetAddresses(t *testing.T) {
 		// Create a user.
 		userID, _, err := s.CreateUser("user", password)
 		require.NoError(t, err)
-		addrID2, err := s.CreateAddress(userID, "user@external.com", []byte("password"))
+		addrID2, err := s.CreateAddress(userID, "user@external.com", password, false)
 		require.NoError(t, err)
 		require.NoError(t, s.ChangeAddressType(userID, addrID2, proton.AddressTypeExternal))
 
@@ -720,6 +720,29 @@ func TestBridge_User_GetAddresses(t *testing.T) {
 	})
 }
 
+func TestBridge_User_GetAddresses_BYOE(t *testing.T) {
+	withEnv(t, func(ctx context.Context, s *server.Server, netCtl *proton.NetCtl, locator bridge.Locator, storeKey []byte) {
+		// Create a user.
+		userID, _, err := s.CreateUser("user", password)
+		require.NoError(t, err)
+		// Add a non-sending external address.
+		_, err = s.CreateExternalAddress(userID, "user@external.com", password, false)
+		require.NoError(t, err)
+		// Add a BYOE address.
+		_, err = s.CreateExternalAddress(userID, "user2@external.com", password, true)
+		require.NoError(t, err)
+
+		withBridge(ctx, t, s.GetHostURL(), netCtl, locator, storeKey, func(bridge *bridge.Bridge, _ *bridge.Mocks) {
+			userLoginAndSync(ctx, t, bridge, "user", password)
+			info, err := bridge.GetUserInfo(userID)
+			require.NoError(t, err)
+			require.Equal(t, 2, len(info.Addresses))
+			require.Equal(t, info.Addresses[0], "user@proton.local")
+			require.Equal(t, info.Addresses[1], "user2@external.com")
+		})
+	})
+}
+
 // getErr returns the error that was passed to it.
 func getErr[T any](_ T, err error) error {
 	return err

internal/dialer/dialer_pinning_test.go

@@ -91,13 +91,12 @@ func TestTLSSignedCertWrongPublicKey(t *testing.T) {
 	r.Error(t, err, "expected dial to fail because of wrong public key")
 }
 
-// GODT-2293 bump badssl cert and re enable this.
-func _TestTLSSignedCertTrustedPublicKey(t *testing.T) { //nolint:unused,deadcode
+func TestTLSSignedCertTrustedPublicKey(t *testing.T) {
 	skipIfProxyIsSet(t)
 
 	_, dialer, _, checker, _ := createClientWithPinningDialer("")
 	copyTrustedPins(checker)
-	checker.trustedPins = append(checker.trustedPins, `pin-sha256="LwnIKjNLV3z243ap8y0yXNPghsqE76J08Eq3COvUt2E="`)
+	checker.trustedPins = append(checker.trustedPins, `pin-sha256="FlvTPG/nIMKtOj9nelnEjujwSZ5EDyfiKYxZgbXREls="`)
 	_, err := dialer.DialTLSContext(context.Background(), "tcp", "rsa4096.badssl.com:443")
 	r.NoError(t, err, "expected dial to succeed because public key is known and cert is signed by CA")
 }

internal/frontend/bridge-gui/bridge-gui/qml/SetupWizard/Login.qml

@@ -271,7 +271,10 @@ FocusScope {
                         usernameTextField.enabled = false;
                         passwordTextField.enabled = false;
                         loading = true;
-                        Backend.login(usernameTextField.text, Qt.btoa(passwordTextField.text));
+
+                        let usernameTextFiltered = usernameTextField.text.replace(/[\n\r]+$/, "");
+                        let passwordTextFiltered = passwordTextField.text.replace(/[\n\r]+$/, "");
+                        Backend.login(usernameTextFiltered, Qt.btoa(passwordTextFiltered));
                     }
 
                     Layout.fillWidth: true

internal/services/imapservice/conflicts.go

@@ -0,0 +1,211 @@
+// Copyright (c) 2025 Proton AG
+//
+// This file is part of Proton Mail Bridge.
+//
+// Proton Mail Bridge is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Proton Mail Bridge is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Proton Mail Bridge.  If not, see <https://www.gnu.org/licenses/>.
+
+package imapservice
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"strings"
+
+	"github.com/ProtonMail/gluon/db"
+	"github.com/ProtonMail/gluon/imap"
+	"github.com/ProtonMail/gluon/reporter"
+	"github.com/ProtonMail/go-proton-api"
+	"github.com/ProtonMail/proton-bridge/v3/internal/unleash"
+	"github.com/sirupsen/logrus"
+)
+
+type GluonLabelNameProvider interface {
+	GetUserMailboxByName(ctx context.Context, addrID string, labelName []string) (imap.MailboxData, error)
+}
+
+type gluonIDProvider interface {
+	GetGluonID(addrID string) (string, bool)
+}
+
+type sentryReporter interface {
+	ReportMessageWithContext(string, reporter.Context) error
+}
+
+type apiClient interface {
+	GetLabel(ctx context.Context, labelID string, labelTypes ...proton.LabelType) (proton.Label, error)
+}
+
+type mailboxFetcherFn func(ctx context.Context, label proton.Label) (imap.MailboxData, error)
+
+type LabelConflictManager struct {
+	gluonLabelNameProvider GluonLabelNameProvider
+	gluonIDProvider        gluonIDProvider
+	client                 apiClient
+	reporter               sentryReporter
+	getFeatureFlagValueFn  unleash.GetFlagValueFn
+}
+
+func NewLabelConflictManager(
+	gluonLabelNameProvider GluonLabelNameProvider,
+	gluonIDProvider gluonIDProvider,
+	client apiClient,
+	reporter sentryReporter,
+	getFeatureFlagValueFn unleash.GetFlagValueFn) *LabelConflictManager {
+	return &LabelConflictManager{
+		gluonLabelNameProvider: gluonLabelNameProvider,
+		gluonIDProvider:        gluonIDProvider,
+		client:                 client,
+		reporter:               reporter,
+		getFeatureFlagValueFn:  getFeatureFlagValueFn,
+	}
+}
+
+func (m *LabelConflictManager) generateMailboxFetcher(connectors []*Connector) mailboxFetcherFn {
+	return func(ctx context.Context, label proton.Label) (imap.MailboxData, error) {
+		for _, updateCh := range connectors {
+			addrID, ok := m.gluonIDProvider.GetGluonID(updateCh.addrID)
+			if !ok {
+				continue
+			}
+			return m.gluonLabelNameProvider.GetUserMailboxByName(ctx, addrID, GetMailboxName(label))
+		}
+		return imap.MailboxData{}, errors.New("no gluon connectors found")
+	}
+}
+
+type LabelConflictResolver interface {
+	ResolveConflict(ctx context.Context, label proton.Label, visited map[string]bool) (func() []imap.Update, error)
+}
+type labelConflictResolverImpl struct {
+	mailboxFetch mailboxFetcherFn
+	client       apiClient
+	reporter     sentryReporter
+}
+
+type nullLabelConflictResolverImpl struct {
+}
+
+func (r *nullLabelConflictResolverImpl) ResolveConflict(_ context.Context, _ proton.Label, _ map[string]bool) (func() []imap.Update, error) {
+	return func() []imap.Update {
+		return []imap.Update{}
+	}, nil
+}
+
+func (m *LabelConflictManager) NewConflictResolver(connectors []*Connector) LabelConflictResolver {
+	if m.getFeatureFlagValueFn(unleash.LabelConflictResolverDisabled) {
+		return &nullLabelConflictResolverImpl{}
+	}
+
+	return &labelConflictResolverImpl{
+		mailboxFetch: m.generateMailboxFetcher(connectors),
+		client:       m.client,
+		reporter:     m.reporter,
+	}
+}
+
+func (r *labelConflictResolverImpl) ResolveConflict(ctx context.Context, label proton.Label, visited map[string]bool) (func() []imap.Update, error) {
+	var updateFns []func() []imap.Update
+
+	// There's a cycle, such as in a label swap operation, we'll need to temporarily rename the label.
+	// The change will be overwritten by one of the previous recursive calls.
+	if visited[label.ID] {
+		fn := func() []imap.Update {
+			return []imap.Update{newMailboxUpdatedOrCreated(imap.MailboxID(label.ID), getMailboxNameWithTempPrefix(label))}
+		}
+		updateFns = append(updateFns, fn)
+		return combineIMAPUpdateFns(updateFns), nil
+	}
+	visited[label.ID] = true
+
+	// Fetch the gluon mailbox data and verify whether there are conflicts with the name.
+	mailboxData, err := r.mailboxFetch(ctx, label)
+	if err != nil {
+		// Name is free, create the mailbox.
+		if db.IsErrNotFound(err) {
+			fn := func() []imap.Update {
+				return []imap.Update{newMailboxUpdatedOrCreated(imap.MailboxID(label.ID), GetMailboxName(label))}
+			}
+			updateFns = append(updateFns, fn)
+			return combineIMAPUpdateFns(updateFns), nil
+		}
+		return combineIMAPUpdateFns(updateFns), err
+	}
+
+	// Verify whether the label name corresponds to the same label ID. If true terminate, we don't need to update.
+	if mailboxData.RemoteID == label.ID {
+		return combineIMAPUpdateFns(updateFns), nil
+	}
+
+	// If the label name belongs to some other label ID. Fetch it's state from the remote.
+	conflictingLabel, err := r.client.GetLabel(ctx, mailboxData.RemoteID, proton.LabelTypeFolder, proton.LabelTypeLabel)
+	if err != nil {
+		// If it's not present on the remote we should delete it. And create the new label.
+		if errors.Is(err, proton.ErrNoSuchLabel) {
+			fn := func() []imap.Update {
+				return []imap.Update{
+					imap.NewMailboxDeleted(imap.MailboxID(mailboxData.RemoteID)),
+					newMailboxUpdatedOrCreated(imap.MailboxID(label.ID), GetMailboxName(label)),
+				}
+			}
+			updateFns = append(updateFns, fn)
+			return combineIMAPUpdateFns(updateFns), nil
+		}
+		return combineIMAPUpdateFns(updateFns), err
+	}
+
+	// Check if the conflicting label name has changed. If not, then this is a BE inconsistency.
+	if compareLabelNames(GetMailboxName(conflictingLabel), mailboxData.BridgeName) {
+		if err := r.reporter.ReportMessageWithContext("Unexpected label conflict", reporter.Context{
+			"labelID":            label.ID,
+			"conflictingLabelID": conflictingLabel.ID,
+		}); err != nil {
+			logrus.WithError(err).Error("Failed to report update error")
+		}
+
+		err := fmt.Errorf("unexpected label conflict: the name of label ID %s is already used by label ID %s", label.ID, conflictingLabel.ID)
+		return combineIMAPUpdateFns(updateFns), err
+	}
+
+	// The name of the conflicting label has changed on the remote. We need to verify that the new name does not conflict with anything else.
+	// Thus, a recursive check can be performed.
+	childUpdateFns, err := r.ResolveConflict(ctx, conflictingLabel, visited)
+	if err != nil {
+		return combineIMAPUpdateFns(updateFns), err
+	}
+	updateFns = append(updateFns, childUpdateFns)
+
+	fn := func() []imap.Update {
+		return []imap.Update{newMailboxUpdatedOrCreated(imap.MailboxID(label.ID), GetMailboxName(label))}
+	}
+	updateFns = append(updateFns, fn)
+
+	return combineIMAPUpdateFns(updateFns), nil
+}
+
+func combineIMAPUpdateFns(updateFunctions []func() []imap.Update) func() []imap.Update {
+	return func() []imap.Update {
+		var updates []imap.Update
+		for _, fn := range updateFunctions {
+			updates = append(updates, fn()...)
+		}
+		return updates
+	}
+}
+
+func compareLabelNames(labelName1, labelName2 []string) bool {
+	name1 := strings.Join(labelName1, "")
+	name2 := strings.Join(labelName2, "")
+	return name1 == name2
+}

internal/services/imapservice/conflicts_test.go

@@ -0,0 +1,682 @@
+// Copyright (c) 2025 Proton AG
+//
+// This file is part of Proton Mail Bridge.
+//
+// Proton Mail Bridge is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Proton Mail Bridge is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Proton Mail Bridge.  If not, see <https://www.gnu.org/licenses/>.
+
+package imapservice_test
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"testing"
+
+	"github.com/ProtonMail/gluon/db"
+	"github.com/ProtonMail/gluon/imap"
+	"github.com/ProtonMail/gluon/reporter"
+	"github.com/ProtonMail/go-proton-api"
+	"github.com/ProtonMail/proton-bridge/v3/internal/services/imapservice"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/mock"
+	"github.com/stretchr/testify/require"
+)
+
+func getFeatureFlagValueMock(_ string) bool {
+	return false
+}
+
+type mockLabelNameProvider struct {
+	mock.Mock
+}
+
+func (m *mockLabelNameProvider) GetUserMailboxByName(ctx context.Context, addrID string, labelName []string) (imap.MailboxData, error) {
+	args := m.Called(ctx, addrID, labelName)
+	v, ok := args.Get(0).(imap.MailboxData)
+	if !ok {
+		return imap.MailboxData{}, fmt.Errorf("failed to assert type")
+	}
+	return v, args.Error(1)
+}
+
+type mockIDProvider struct {
+	mock.Mock
+}
+
+func (m *mockIDProvider) GetGluonID(addrID string) (string, bool) {
+	args := m.Called(addrID)
+	return args.String(0), args.Bool(1)
+}
+
+type mockAPIClient struct {
+	mock.Mock
+}
+
+func (m *mockAPIClient) GetLabel(ctx context.Context, id string, types ...proton.LabelType) (proton.Label, error) {
+	args := m.Called(ctx, id, types)
+	v, ok := args.Get(0).(proton.Label)
+	if !ok {
+		return proton.Label{}, fmt.Errorf("failed to assert type")
+	}
+	return v, args.Error(1)
+}
+
+type mockReporter struct {
+	mock.Mock
+}
+
+func (m *mockReporter) ReportMessageWithContext(msg string, ctx reporter.Context) error {
+	args := m.Called(msg, ctx)
+	return args.Error(0)
+}
+
+func TestResolveConflict_UnexpectedLabelConflict(t *testing.T) {
+	ctx := context.Background()
+	label := proton.Label{
+		ID:   "label-1",
+		Path: []string{"Work"},
+		Type: proton.LabelTypeLabel,
+	}
+	conflictingLabel := proton.Label{
+		ID:   "label-2",
+		Path: []string{"Work"},
+		Type: proton.LabelTypeLabel,
+	}
+	conflictMbox := imap.MailboxData{
+		RemoteID:   "label-2",
+		BridgeName: []string{"Labels", "Work"},
+	}
+
+	mockLabelProvider := new(mockLabelNameProvider)
+	mockIDProvider := new(mockIDProvider)
+	mockClient := new(mockAPIClient)
+	mockReporter := new(mockReporter)
+
+	mockLabelProvider.On("GetUserMailboxByName", mock.Anything, "gluon-id", imapservice.GetMailboxName(label)).
+		Return(conflictMbox, nil)
+	mockIDProvider.On("GetGluonID", "addr-1").Return("gluon-id", true)
+	mockClient.On("GetLabel", mock.Anything, "label-2", mock.Anything).
+		Return(conflictingLabel, nil)
+	mockReporter.On("ReportMessageWithContext", "Unexpected label conflict", mock.Anything).
+		Return(nil)
+
+	connector := &imapservice.Connector{}
+	connector.SetAddrIDTest("addr-1")
+	resolver := imapservice.NewLabelConflictManager(mockLabelProvider, mockIDProvider, mockClient, mockReporter, getFeatureFlagValueMock).
+		NewConflictResolver([]*imapservice.Connector{connector})
+
+	visited := make(map[string]bool)
+	_, err := resolver.ResolveConflict(ctx, label, visited)
+	assert.Error(t, err)
+	assert.Contains(t, err.Error(), "unexpected label conflict")
+}
+
+func TestResolveDiscrepancy_LabelDoesNotExist(t *testing.T) {
+	ctx := context.Background()
+	label := proton.Label{
+		ID:   "label-id-1",
+		Name: "Inbox",
+		Type: proton.LabelTypeLabel,
+	}
+
+	mockLabelProvider := new(mockLabelNameProvider)
+	mockIDProvider := new(mockIDProvider)
+	mockClient := new(mockAPIClient)
+	mockReporter := new(mockReporter)
+
+	mockLabelProvider.On("GetUserMailboxByName", mock.Anything, "gluon-id-1", imapservice.GetMailboxName(label)).
+		Return(imap.MailboxData{}, db.ErrNotFound)
+
+	mockIDProvider.On("GetGluonID", "addr-1").Return("gluon-id-1", true)
+
+	connector := &imapservice.Connector{}
+	connector.SetAddrIDTest("addr-1")
+	connectors := []*imapservice.Connector{connector}
+
+	manager := imapservice.NewLabelConflictManager(mockLabelProvider, mockIDProvider, mockClient, mockReporter, getFeatureFlagValueMock)
+	resolver := manager.NewConflictResolver(connectors)
+
+	visited := make(map[string]bool)
+	fn, err := resolver.ResolveConflict(ctx, label, visited)
+
+	assert.NoError(t, err)
+	updates := fn()
+	assert.Len(t, updates, 1)
+	muc, ok := updates[0].(*imap.MailboxUpdatedOrCreated)
+	assert.True(t, ok)
+	assert.Equal(t, imap.MailboxID(label.ID), muc.Mailbox.ID)
+}
+
+func TestResolveConflict_MailboxFetchError(t *testing.T) {
+	ctx := context.Background()
+	label := proton.Label{
+		ID:   "111",
+		Path: []string{"Work"},
+		Type: proton.LabelTypeLabel,
+	}
+
+	mockLabelProvider := new(mockLabelNameProvider)
+	mockIDProvider := new(mockIDProvider)
+	mockClient := new(mockAPIClient)
+	mockReporter := new(mockReporter)
+
+	mockLabelProvider.On("GetUserMailboxByName", mock.Anything, "gluon-id", imapservice.GetMailboxName(label)).
+		Return(imap.MailboxData{}, errors.New("database connection error"))
+	mockIDProvider.On("GetGluonID", "addr-1").Return("gluon-id", true)
+
+	connector := &imapservice.Connector{}
+	connector.SetAddrIDTest("addr-1")
+	resolver := imapservice.NewLabelConflictManager(mockLabelProvider, mockIDProvider, mockClient, mockReporter, getFeatureFlagValueMock).
+		NewConflictResolver([]*imapservice.Connector{connector})
+
+	visited := make(map[string]bool)
+	_, err := resolver.ResolveConflict(ctx, label, visited)
+	assert.Error(t, err)
+	assert.Contains(t, err.Error(), "database connection error")
+}
+
+func TestResolveDiscrepancy_ConflictingLabelDeletedRemotely(t *testing.T) {
+	ctx := context.Background()
+	label := proton.Label{
+		ID:   "label-new",
+		Path: []string{"Work"},
+		Type: proton.LabelTypeLabel,
+	}
+	conflictMbox := imap.MailboxData{
+		RemoteID:   "label-old",
+		BridgeName: []string{"Labels", "Work"},
+	}
+
+	mockLabelProvider := new(mockLabelNameProvider)
+	mockIDProvider := new(mockIDProvider)
+	mockClient := new(mockAPIClient)
+	mockReporter := new(mockReporter)
+
+	mockLabelProvider.On("GetUserMailboxByName", mock.Anything, "gluon-id-1", imapservice.GetMailboxName(label)).
+		Return(conflictMbox, nil)
+
+	mockIDProvider.On("GetGluonID", "addr-1").Return("gluon-id-1", true)
+
+	mockClient.On("GetLabel", mock.Anything, "label-old", mock.Anything).
+		Return(proton.Label{}, proton.ErrNoSuchLabel)
+
+	connector := &imapservice.Connector{}
+	connector.SetAddrIDTest("addr-1")
+	connectors := []*imapservice.Connector{connector}
+
+	manager := imapservice.NewLabelConflictManager(mockLabelProvider, mockIDProvider, mockClient, mockReporter, getFeatureFlagValueMock)
+	resolver := manager.NewConflictResolver(connectors)
+
+	visited := make(map[string]bool)
+	fn, err := resolver.ResolveConflict(ctx, label, visited)
+
+	assert.NoError(t, err)
+	updates := fn()
+	assert.Len(t, updates, 2)
+	deleted, ok := updates[0].(*imap.MailboxDeleted)
+	assert.True(t, ok)
+	assert.Equal(t, imap.MailboxID("label-old"), deleted.MailboxID)
+
+	updated, ok := updates[1].(*imap.MailboxUpdatedOrCreated)
+	assert.True(t, ok)
+	assert.Equal(t, "Work", updated.Mailbox.Name[len(updated.Mailbox.Name)-1])
+}
+
+func TestResolveDiscrepancy_LabelAlreadyCorrect(t *testing.T) {
+	ctx := context.Background()
+	label := proton.Label{
+		ID:   "label-id-1",
+		Name: "Personal",
+		Type: proton.LabelTypeLabel,
+	}
+	mbox := imap.MailboxData{
+		RemoteID:   "label-id-1",
+		BridgeName: []string{"Labels", "Personal"},
+	}
+
+	mockLabelProvider := new(mockLabelNameProvider)
+	mockIDProvider := new(mockIDProvider)
+	mockClient := new(mockAPIClient)
+	mockReporter := new(mockReporter)
+
+	mockLabelProvider.On("GetUserMailboxByName", mock.Anything, "gluon-id-1", imapservice.GetMailboxName(label)).
+		Return(mbox, nil)
+	mockIDProvider.On("GetGluonID", "addr-1").Return("gluon-id-1", true)
+
+	connector := &imapservice.Connector{}
+	connector.SetAddrIDTest("addr-1")
+	connectors := []*imapservice.Connector{connector}
+
+	manager := imapservice.NewLabelConflictManager(mockLabelProvider, mockIDProvider, mockClient, mockReporter, getFeatureFlagValueMock)
+	resolver := manager.NewConflictResolver(connectors)
+
+	visited := make(map[string]bool)
+	fn, err := resolver.ResolveConflict(ctx, label, visited)
+
+	assert.NoError(t, err)
+	assert.Len(t, fn(), 0)
+}
+
+func TestResolveConflict_DeepNestedPath(t *testing.T) {
+	ctx := context.Background()
+	label := proton.Label{
+		ID:   "111",
+		Path: []string{"Level1", "Level2", "Level3", "DeepFolder"},
+		Type: proton.LabelTypeFolder,
+	}
+
+	mockLabelProvider := new(mockLabelNameProvider)
+	mockIDProvider := new(mockIDProvider)
+	mockClient := new(mockAPIClient)
+	mockReporter := new(mockReporter)
+
+	mockLabelProvider.On("GetUserMailboxByName", mock.Anything, "gluon-id", imapservice.GetMailboxName(label)).
+		Return(imap.MailboxData{}, db.ErrNotFound)
+	mockIDProvider.On("GetGluonID", "addr-1").Return("gluon-id", true)
+
+	connector := &imapservice.Connector{}
+	connector.SetAddrIDTest("addr-1")
+	resolver := imapservice.NewLabelConflictManager(mockLabelProvider, mockIDProvider, mockClient, mockReporter, getFeatureFlagValueMock).
+		NewConflictResolver([]*imapservice.Connector{connector})
+
+	visited := make(map[string]bool)
+	fn, err := resolver.ResolveConflict(ctx, label, visited)
+
+	assert.NoError(t, err)
+	updates := fn()
+	assert.Len(t, updates, 1)
+
+	updated, ok := updates[0].(*imap.MailboxUpdatedOrCreated)
+	assert.True(t, ok)
+	assert.Equal(t, imap.MailboxID("111"), updated.Mailbox.ID)
+	expectedName := imapservice.GetMailboxName(label)
+	assert.Equal(t, expectedName, updated.Mailbox.Name)
+}
+
+func TestResolveLabelDiscrepancy_LabelSwap(t *testing.T) {
+	apiLabels := []proton.Label{
+		{
+			ID:   "111",
+			Path: []string{"X"},
+			Type: proton.LabelTypeLabel,
+		},
+		{
+			ID:   "222",
+			Path: []string{"Y"},
+			Type: proton.LabelTypeLabel,
+		},
+	}
+
+	gluonLabels := []imap.MailboxData{
+		{
+			RemoteID:   "111",
+			BridgeName: []string{"Labels", "Y"},
+		},
+		{
+			RemoteID:   "222",
+			BridgeName: []string{"Labels", "X"},
+		},
+	}
+
+	mockLabelProvider := new(mockLabelNameProvider)
+	mockClient := new(mockAPIClient)
+	mockIDProvider := new(mockIDProvider)
+	mockReporter := new(mockReporter)
+
+	mockIDProvider.On("GetGluonID", "addr-1").Return("gluon-id-1", true)
+
+	for _, mbox := range gluonLabels {
+		mockLabelProvider.
+			On("GetUserMailboxByName", mock.Anything, "gluon-id-1", mbox.BridgeName).
+			Return(mbox, nil)
+	}
+
+	for _, label := range apiLabels {
+		mockClient.
+			On("GetLabel", mock.Anything, label.ID, []proton.LabelType{proton.LabelTypeFolder, proton.LabelTypeLabel}).
+			Return(label, nil)
+	}
+
+	connector := &imapservice.Connector{}
+	connector.SetAddrIDTest("addr-1")
+	connectors := []*imapservice.Connector{connector}
+
+	manager := imapservice.NewLabelConflictManager(mockLabelProvider, mockIDProvider, mockClient, mockReporter, getFeatureFlagValueMock)
+	resolver := manager.NewConflictResolver(connectors)
+
+	visited := make(map[string]bool)
+	fn, err := resolver.ResolveConflict(context.Background(), apiLabels[0], visited)
+	require.NoError(t, err)
+
+	updates := fn()
+	assert.NotEmpty(t, updates)
+	assert.Equal(t, 3, len(updates)) // We expect three calls to be made for a swap operation.
+
+	updateOne, ok := updates[0].(*imap.MailboxUpdatedOrCreated)
+	assert.True(t, ok)
+	assert.Equal(t, imap.MailboxID(apiLabels[0].ID), updateOne.Mailbox.ID)
+	assert.Equal(t, "tmp_X", updateOne.Mailbox.Name[len(updateOne.Mailbox.Name)-1])
+
+	updateTwo, ok := updates[1].(*imap.MailboxUpdatedOrCreated)
+	assert.True(t, ok)
+	assert.Equal(t, imap.MailboxID(apiLabels[1].ID), updateTwo.Mailbox.ID)
+	assert.Equal(t, "Y", updateTwo.Mailbox.Name[len(updateTwo.Mailbox.Name)-1])
+
+	updateThree, ok := updates[2].(*imap.MailboxUpdatedOrCreated)
+	assert.True(t, ok)
+	assert.Equal(t, imap.MailboxID(apiLabels[0].ID), updateThree.Mailbox.ID)
+	assert.Equal(t, "X", updateThree.Mailbox.Name[len(updateThree.Mailbox.Name)-1])
+}
+
+func TestResolveLabelDiscrepancy_LabelSwapExtended(t *testing.T) {
+	apiLabels := []proton.Label{
+		{
+			ID:   "111",
+			Path: []string{"X"},
+			Type: proton.LabelTypeLabel,
+		},
+		{
+			ID:   "222",
+			Path: []string{"Y"},
+			Type: proton.LabelTypeLabel,
+		},
+		{
+			ID:   "333",
+			Path: []string{"Z"},
+			Type: proton.LabelTypeLabel,
+		},
+		{
+			ID:   "444",
+			Path: []string{"D"},
+			Type: proton.LabelTypeLabel,
+		},
+	}
+
+	gluonLabels := []imap.MailboxData{
+		{
+			RemoteID:   "111",
+			BridgeName: []string{"Labels", "D"},
+		},
+		{
+			RemoteID:   "222",
+			BridgeName: []string{"Labels", "Z"},
+		},
+		{
+			RemoteID:   "333",
+			BridgeName: []string{"Labels", "Y"},
+		},
+		{
+			RemoteID:   "444",
+			BridgeName: []string{"Labels", "X"},
+		},
+	}
+
+	mockLabelProvider := new(mockLabelNameProvider)
+	mockClient := new(mockAPIClient)
+	mockIDProvider := new(mockIDProvider)
+	mockReporter := new(mockReporter)
+
+	mockIDProvider.On("GetGluonID", "addr-1").Return("gluon-id-1", true)
+
+	for _, mbox := range gluonLabels {
+		mockLabelProvider.
+			On("GetUserMailboxByName", mock.Anything, "gluon-id-1", mbox.BridgeName).
+			Return(mbox, nil)
+	}
+
+	for _, label := range apiLabels {
+		mockClient.
+			On("GetLabel", mock.Anything, label.ID, []proton.LabelType{proton.LabelTypeFolder, proton.LabelTypeLabel}).
+			Return(label, nil)
+	}
+
+	connector := &imapservice.Connector{}
+	connector.SetAddrIDTest("addr-1")
+	connectors := []*imapservice.Connector{connector}
+
+	manager := imapservice.NewLabelConflictManager(mockLabelProvider, mockIDProvider, mockClient, mockReporter, getFeatureFlagValueMock)
+	resolver := manager.NewConflictResolver(connectors)
+
+	fn, err := resolver.ResolveConflict(context.Background(), apiLabels[0], make(map[string]bool))
+	require.NoError(t, err)
+
+	updates := fn()
+	assert.NotEmpty(t, updates)
+	// Three calls yet again for a swap operation.
+	assert.Equal(t, 3, len(updates))
+	updateOne, ok := updates[0].(*imap.MailboxUpdatedOrCreated)
+	assert.True(t, ok)
+	assert.Equal(t, imap.MailboxID(apiLabels[0].ID), updateOne.Mailbox.ID)
+	assert.Equal(t, "tmp_X", updateOne.Mailbox.Name[len(updateOne.Mailbox.Name)-1])
+
+	updateTwo, ok := updates[1].(*imap.MailboxUpdatedOrCreated)
+	assert.True(t, ok)
+	assert.Equal(t, imap.MailboxID(apiLabels[3].ID), updateTwo.Mailbox.ID)
+	assert.Equal(t, "D", updateTwo.Mailbox.Name[len(updateTwo.Mailbox.Name)-1])
+
+	updateThree, ok := updates[2].(*imap.MailboxUpdatedOrCreated)
+	assert.True(t, ok)
+	assert.Equal(t, imap.MailboxID(apiLabels[0].ID), updateThree.Mailbox.ID)
+	assert.Equal(t, "X", updateThree.Mailbox.Name[len(updateThree.Mailbox.Name)-1])
+
+	// Fix the secondary swap.
+	fn, err = resolver.ResolveConflict(context.Background(), apiLabels[1], make(map[string]bool))
+	require.NoError(t, err)
+
+	updates = fn()
+	assert.Equal(t, 3, len(updates))
+	updateOne, ok = updates[0].(*imap.MailboxUpdatedOrCreated)
+	assert.True(t, ok)
+	assert.Equal(t, imap.MailboxID(apiLabels[1].ID), updateOne.Mailbox.ID)
+	assert.Equal(t, "tmp_Y", updateOne.Mailbox.Name[len(updateOne.Mailbox.Name)-1])
+
+	updateTwo, ok = updates[1].(*imap.MailboxUpdatedOrCreated)
+	assert.True(t, ok)
+	assert.Equal(t, imap.MailboxID(apiLabels[2].ID), updateTwo.Mailbox.ID)
+	assert.Equal(t, "Z", updateTwo.Mailbox.Name[len(updateTwo.Mailbox.Name)-1])
+
+	updateThree, ok = updates[2].(*imap.MailboxUpdatedOrCreated)
+	assert.True(t, ok)
+	assert.Equal(t, imap.MailboxID(apiLabels[1].ID), updateThree.Mailbox.ID)
+	assert.Equal(t, "Y", updateThree.Mailbox.Name[len(updateThree.Mailbox.Name)-1])
+}
+
+func TestResolveLabelDiscrepancy_LabelSwapCyclic(t *testing.T) {
+	apiLabels := []proton.Label{
+		{ID: "111", Path: []string{"A"}, Type: proton.LabelTypeLabel},
+		{ID: "222", Path: []string{"B"}, Type: proton.LabelTypeLabel},
+		{ID: "333", Path: []string{"C"}, Type: proton.LabelTypeLabel},
+		{ID: "444", Path: []string{"D"}, Type: proton.LabelTypeLabel},
+	}
+
+	gluonLabels := []imap.MailboxData{
+		{RemoteID: "111", BridgeName: []string{"Labels", "D"}}, // A <- D
+		{RemoteID: "222", BridgeName: []string{"Labels", "A"}}, // B <- A
+		{RemoteID: "333", BridgeName: []string{"Labels", "B"}}, // C <- B
+		{RemoteID: "444", BridgeName: []string{"Labels", "C"}}, // D <- C
+	}
+
+	mockLabelProvider := new(mockLabelNameProvider)
+	mockClient := new(mockAPIClient)
+	mockIDProvider := new(mockIDProvider)
+	mockReporter := new(mockReporter)
+
+	mockIDProvider.On("GetGluonID", "addr-1").Return("gluon-id-1", true)
+
+	for _, mbox := range gluonLabels {
+		mockLabelProvider.
+			On("GetUserMailboxByName", mock.Anything, "gluon-id-1", mbox.BridgeName).
+			Return(mbox, nil)
+	}
+
+	for _, label := range apiLabels {
+		mockClient.
+			On("GetLabel", mock.Anything, label.ID, []proton.LabelType{proton.LabelTypeFolder, proton.LabelTypeLabel}).
+			Return(label, nil)
+	}
+
+	connector := &imapservice.Connector{}
+	connector.SetAddrIDTest("addr-1")
+	connectors := []*imapservice.Connector{connector}
+
+	manager := imapservice.NewLabelConflictManager(mockLabelProvider, mockIDProvider, mockClient, mockReporter, getFeatureFlagValueMock)
+	resolver := manager.NewConflictResolver(connectors)
+
+	fn, err := resolver.ResolveConflict(context.Background(), apiLabels[0], make(map[string]bool))
+	require.NoError(t, err)
+
+	updates := fn()
+	assert.NotEmpty(t, updates)
+	assert.Equal(t, 5, len(updates))
+
+	updateOne, ok := updates[0].(*imap.MailboxUpdatedOrCreated)
+	assert.True(t, ok)
+	assert.Equal(t, imap.MailboxID(apiLabels[0].ID), updateOne.Mailbox.ID)
+	assert.Equal(t, "tmp_A", updateOne.Mailbox.Name[len(updateOne.Mailbox.Name)-1])
+
+	updateTwo, ok := updates[1].(*imap.MailboxUpdatedOrCreated)
+	assert.True(t, ok)
+	assert.Equal(t, imap.MailboxID(apiLabels[3].ID), updateTwo.Mailbox.ID)
+	assert.Equal(t, "D", updateTwo.Mailbox.Name[len(updateTwo.Mailbox.Name)-1])
+
+	updateThree, ok := updates[2].(*imap.MailboxUpdatedOrCreated)
+	assert.True(t, ok)
+	assert.Equal(t, imap.MailboxID(apiLabels[2].ID), updateThree.Mailbox.ID)
+	assert.Equal(t, "C", updateThree.Mailbox.Name[len(updateThree.Mailbox.Name)-1])
+
+	updateFour, ok := updates[3].(*imap.MailboxUpdatedOrCreated)
+	assert.True(t, ok)
+	assert.Equal(t, imap.MailboxID(apiLabels[1].ID), updateFour.Mailbox.ID)
+	assert.Equal(t, "B", updateFour.Mailbox.Name[len(updateFour.Mailbox.Name)-1])
+
+	updateFive, ok := updates[4].(*imap.MailboxUpdatedOrCreated)
+	assert.True(t, ok)
+	assert.Equal(t, imap.MailboxID(apiLabels[0].ID), updateFive.Mailbox.ID)
+	assert.Equal(t, "A", updateFive.Mailbox.Name[len(updateFive.Mailbox.Name)-1])
+}
+
+func TestResolveLabelDiscrepancy_LabelSwapCyclicWithDeletedLabel(t *testing.T) {
+	apiLabels := []proton.Label{
+		{ID: "111", Path: []string{"A"}, Type: proton.LabelTypeLabel},
+		{ID: "333", Path: []string{"C"}, Type: proton.LabelTypeLabel},
+		{ID: "444", Path: []string{"D"}, Type: proton.LabelTypeLabel},
+	}
+
+	gluonLabels := []imap.MailboxData{
+		{RemoteID: "111", BridgeName: []string{"Labels", "D"}},
+		{RemoteID: "222", BridgeName: []string{"Labels", "A"}},
+		{RemoteID: "333", BridgeName: []string{"Labels", "B"}},
+		{RemoteID: "444", BridgeName: []string{"Labels", "C"}},
+	}
+
+	mockLabelProvider := new(mockLabelNameProvider)
+	mockClient := new(mockAPIClient)
+	mockIDProvider := new(mockIDProvider)
+	mockReporter := new(mockReporter)
+
+	mockIDProvider.On("GetGluonID", "addr-1").Return("gluon-id-1", true)
+
+	for _, mbox := range gluonLabels {
+		mockLabelProvider.
+			On("GetUserMailboxByName", mock.Anything, "gluon-id-1", mbox.BridgeName).
+			Return(mbox, nil)
+	}
+
+	for _, label := range apiLabels {
+		mockClient.
+			On("GetLabel", mock.Anything, label.ID, []proton.LabelType{proton.LabelTypeFolder, proton.LabelTypeLabel}).
+			Return(label, nil)
+	}
+	mockClient.On("GetLabel", mock.Anything, "222", []proton.LabelType{proton.LabelTypeFolder, proton.LabelTypeLabel}).Return(proton.Label{}, proton.ErrNoSuchLabel)
+
+	connector := &imapservice.Connector{}
+	connector.SetAddrIDTest("addr-1")
+	connectors := []*imapservice.Connector{connector}
+
+	manager := imapservice.NewLabelConflictManager(mockLabelProvider, mockIDProvider, mockClient, mockReporter, getFeatureFlagValueMock)
+	resolver := manager.NewConflictResolver(connectors)
+
+	fn, err := resolver.ResolveConflict(context.Background(), apiLabels[2], make(map[string]bool))
+	require.NoError(t, err)
+
+	updates := fn()
+	assert.NotEmpty(t, updates)
+	assert.Equal(t, 3, len(updates))
+
+	updateOne, ok := updates[0].(*imap.MailboxDeleted)
+	assert.True(t, ok)
+	assert.Equal(t, imap.MailboxID("222"), updateOne.MailboxID)
+
+	updateTwo, ok := updates[1].(*imap.MailboxUpdatedOrCreated)
+	assert.True(t, ok)
+	assert.Equal(t, imap.MailboxID(apiLabels[0].ID), updateTwo.Mailbox.ID)
+	assert.Equal(t, "A", updateTwo.Mailbox.Name[len(updateTwo.Mailbox.Name)-1])
+
+	updateThree, ok := updates[2].(*imap.MailboxUpdatedOrCreated)
+	assert.True(t, ok)
+	assert.Equal(t, imap.MailboxID(apiLabels[2].ID), updateThree.Mailbox.ID)
+	assert.Equal(t, "D", updateThree.Mailbox.Name[len(updateThree.Mailbox.Name)-1])
+}
+
+func TestResolveLabelDiscrepancy_LabelSwapCyclicWithDeletedLabel_KillSwitchEnabled(t *testing.T) {
+	apiLabels := []proton.Label{
+		{ID: "111", Path: []string{"A"}, Type: proton.LabelTypeLabel},
+		{ID: "333", Path: []string{"C"}, Type: proton.LabelTypeLabel},
+		{ID: "444", Path: []string{"D"}, Type: proton.LabelTypeLabel},
+	}
+
+	gluonLabels := []imap.MailboxData{
+		{RemoteID: "111", BridgeName: []string{"Labels", "D"}},
+		{RemoteID: "222", BridgeName: []string{"Labels", "A"}},
+		{RemoteID: "333", BridgeName: []string{"Labels", "B"}},
+		{RemoteID: "444", BridgeName: []string{"Labels", "C"}},
+	}
+
+	mockLabelProvider := new(mockLabelNameProvider)
+	mockClient := new(mockAPIClient)
+	mockIDProvider := new(mockIDProvider)
+	mockReporter := new(mockReporter)
+
+	mockIDProvider.On("GetGluonID", "addr-1").Return("gluon-id-1", true)
+
+	for _, mbox := range gluonLabels {
+		mockLabelProvider.
+			On("GetUserMailboxByName", mock.Anything, "gluon-id-1", mbox.BridgeName).
+			Return(mbox, nil)
+	}
+
+	for _, label := range apiLabels {
+		mockClient.
+			On("GetLabel", mock.Anything, label.ID, []proton.LabelType{proton.LabelTypeFolder, proton.LabelTypeLabel}).
+			Return(label, nil)
+	}
+	mockClient.On("GetLabel", mock.Anything, "222", []proton.LabelType{proton.LabelTypeFolder, proton.LabelTypeLabel}).Return(proton.Label{}, proton.ErrNoSuchLabel)
+
+	connector := &imapservice.Connector{}
+	connector.SetAddrIDTest("addr-1")
+	connectors := []*imapservice.Connector{connector}
+
+	getFeatureFlagFn := func(_ string) bool {
+		return true
+	}
+
+	manager := imapservice.NewLabelConflictManager(mockLabelProvider, mockIDProvider, mockClient, mockReporter, getFeatureFlagFn)
+	resolver := manager.NewConflictResolver(connectors)
+
+	fn, err := resolver.ResolveConflict(context.Background(), apiLabels[2], make(map[string]bool))
+	require.NoError(t, err)
+
+	updates := fn()
+	assert.Empty(t, updates)
+}

internal/services/imapservice/connector.go

@@ -257,7 +257,7 @@ func (s *Connector) DeleteMailbox(ctx context.Context, _ connector.IMAPStateWrit
 	wLabels := s.labels.Write()
 	defer wLabels.Close()
 
-	wLabels.Delete(string(mboxID))
+	wLabels.Delete(string(mboxID), "connectorDeleteMailbox")
 
 	return nil
 }
@@ -555,7 +555,7 @@ func (s *Connector) createLabel(ctx context.Context, name []string) (imap.Mailbo
 	wLabels := s.labels.Write()
 	defer wLabels.Close()
 
-	wLabels.SetLabel(label.ID, label)
+	wLabels.SetLabel(label.ID, label, "connectorCreateLabel")
 
 	return toIMAPMailbox(label, s.flags, s.permFlags, s.attrs), nil
 }
@@ -593,7 +593,7 @@ func (s *Connector) createFolder(ctx context.Context, name []string) (imap.Mailb
 	}
 
 	// Add label to list so subsequent sub folder create requests work correct.
-	wLabels.SetLabel(label.ID, label)
+	wLabels.SetLabel(label.ID, label, "connectorCreateFolder")
 
 	return toIMAPMailbox(label, s.flags, s.permFlags, s.attrs), nil
 }
@@ -619,7 +619,7 @@ func (s *Connector) updateLabel(ctx context.Context, labelID imap.MailboxID, nam
 	wLabels := s.labels.Write()
 	defer wLabels.Close()
 
-	wLabels.SetLabel(label.ID, update)
+	wLabels.SetLabel(label.ID, update, "connectorUpdateLabel")
 
 	return nil
 }
@@ -660,7 +660,7 @@ func (s *Connector) updateFolder(ctx context.Context, labelID imap.MailboxID, na
 		return err
 	}
 
-	wLabels.SetLabel(label.ID, update)
+	wLabels.SetLabel(label.ID, update, "connectorUpdateFolder")
 
 	return nil
 }
@@ -680,7 +680,7 @@ func (s *Connector) importMessage(
 	}
 
 	isDraft := slices.Contains(labelIDs, proton.DraftsLabel)
-	addr, err := s.getImportAddress(p, isDraft)
+	addr, err := getImportAddress(p, isDraft, s.addrID, s)
 	if err != nil {
 		return imap.Message{}, nil, err
 	}
@@ -800,8 +800,10 @@ func (s *Connector) createDraftWithParser(ctx context.Context, parser *parser.Pa
 	return draft, nil
 }
 
-func (s *Connector) publishUpdate(_ context.Context, update imap.Update) {
-	s.updateCh.Enqueue(update)
+func (s *Connector) publishUpdate(_ context.Context, updates ...imap.Update) {
+	for _, update := range updates {
+		s.updateCh.Enqueue(update)
+	}
 }
 
 func fixGODT3003Labels(
@@ -871,45 +873,6 @@ func equalAddresses(a, b string) bool {
 	return strings.EqualFold(stripPlusAlias(a), stripPlusAlias(b))
 }
 
-func (s *Connector) getImportAddress(p *parser.Parser, isDraft bool) (proton.Address, error) {
-	// addr is primary for combined mode or active for split mode
-	address, ok := s.identityState.GetAddress(s.addrID)
-	if !ok {
-		return proton.Address{}, errors.New("could not find account address")
-	}
-
-	inCombinedMode := s.addressMode == usertypes.AddressModeCombined
-	if !inCombinedMode {
-		return address, nil
-	}
-
-	senderAddr, err := s.getSenderProtonAddress(p)
-	if err != nil {
-		if !errors.Is(err, errNoSenderAddressMatch) {
-			s.log.WithError(err).Warn("Could not get import address")
-		}
-
-		// We did not find a match, so we use the default address.
-		return address, nil
-	}
-
-	if senderAddr.ID == address.ID {
-		return address, nil
-	}
-
-	// GODT-3185 / BRIDGE-120 In combined mode, in certain cases we adapt the address used for encryption.
-	// - draft with non-default address in combined mode: using sender address
-	// - import with non-default address in combined mode: using sender address
-	// - import with non-default disabled address in combined mode: using sender address
-
-	isSenderAddressDisabled := (!bool(senderAddr.Send)) || (senderAddr.Status != proton.AddressStatusEnabled)
-	if isDraft && isSenderAddressDisabled {
-		return address, nil
-	}
-
-	return senderAddr, nil
-}
-
 func (s *Connector) getSenderProtonAddress(p *parser.Parser) (proton.Address, error) {
 	// Step 1: extract sender email address from message
 	if (p == nil) || (p.Root() == nil) || (p.Root().Header.Len() == 0) {
@@ -942,3 +905,7 @@ func (s *Connector) getSenderProtonAddress(p *parser.Parser) (proton.Address, er
 
 	return addressList[index], nil
 }
+
+func (s *Connector) SetAddrIDTest(addrID string) {
+	s.addrID = addrID
+}

internal/services/imapservice/connector_test.go

@@ -43,7 +43,7 @@ func TestFixGODT3003Labels(t *testing.T) {
 		Path:     []string{"bar", "Foo"},
 		Color:    "",
 		Type:     proton.LabelTypeFolder,
-	})
+	}, "")
 
 	wr.SetLabel("0", proton.Label{
 		ID:       "0",
@@ -52,7 +52,7 @@ func TestFixGODT3003Labels(t *testing.T) {
 		Path:     []string{"Inbox"},
 		Color:    "",
 		Type:     proton.LabelTypeSystem,
-	})
+	}, "")
 
 	wr.SetLabel("bar", proton.Label{
 		ID:       "bar",
@@ -61,7 +61,7 @@ func TestFixGODT3003Labels(t *testing.T) {
 		Path:     []string{"bar"},
 		Color:    "",
 		Type:     proton.LabelTypeFolder,
-	})
+	}, "")
 
 	wr.SetLabel("my_label", proton.Label{
 		ID:       "my_label",
@@ -70,7 +70,7 @@ func TestFixGODT3003Labels(t *testing.T) {
 		Path:     []string{"MyLabel"},
 		Color:    "",
 		Type:     proton.LabelTypeLabel,
-	})
+	}, "")
 
 	wr.SetLabel("my_label2", proton.Label{
 		ID:       "my_label2",
@@ -79,7 +79,7 @@ func TestFixGODT3003Labels(t *testing.T) {
 		Path:     []string{labelPrefix, "MyLabel2"},
 		Color:    "",
 		Type:     proton.LabelTypeLabel,
-	})
+	}, "")
 	wr.Close()
 
 	mboxs := []imap.MailboxNoAttrib{
@@ -133,7 +133,7 @@ func TestFixGODT3003Labels_Noop(t *testing.T) {
 		Path:     []string{folderPrefix, "bar", "Foo"},
 		Color:    "",
 		Type:     proton.LabelTypeFolder,
-	})
+	}, "")
 
 	wr.SetLabel("0", proton.Label{
 		ID:       "0",
@@ -142,7 +142,7 @@ func TestFixGODT3003Labels_Noop(t *testing.T) {
 		Path:     []string{"Inbox"},
 		Color:    "",
 		Type:     proton.LabelTypeSystem,
-	})
+	}, "")
 
 	wr.SetLabel("bar", proton.Label{
 		ID:       "bar",
@@ -151,7 +151,7 @@ func TestFixGODT3003Labels_Noop(t *testing.T) {
 		Path:     []string{folderPrefix, "bar"},
 		Color:    "",
 		Type:     proton.LabelTypeFolder,
-	})
+	}, "")
 
 	wr.SetLabel("my_label", proton.Label{
 		ID:       "my_label",
@@ -160,7 +160,7 @@ func TestFixGODT3003Labels_Noop(t *testing.T) {
 		Path:     []string{labelPrefix, "MyLabel"},
 		Color:    "",
 		Type:     proton.LabelTypeLabel,
-	})
+	}, "")
 
 	wr.SetLabel("my_label2", proton.Label{
 		ID:       "my_label2",
@@ -169,7 +169,7 @@ func TestFixGODT3003Labels_Noop(t *testing.T) {
 		Path:     []string{labelPrefix, "MyLabel2"},
 		Color:    "",
 		Type:     proton.LabelTypeLabel,
-	})
+	}, "")
 	wr.Close()
 
 	mboxs := []imap.MailboxNoAttrib{

internal/services/imapservice/imap_updates.go

@@ -102,6 +102,16 @@ func newMailboxCreatedUpdate(labelID imap.MailboxID, labelName []string) *imap.M
 	})
 }
 
+func newMailboxUpdatedOrCreated(labelID imap.MailboxID, labelName []string) *imap.MailboxUpdatedOrCreated {
+	return imap.NewMailboxUpdatedOrCreated(imap.Mailbox{
+		ID:             labelID,
+		Name:           labelName,
+		Flags:          defaultMailboxFlags(),
+		PermanentFlags: defaultMailboxPermanentFlags(),
+		Attributes:     imap.NewFlagSet(),
+	})
+}
+
 func GetMailboxName(label proton.Label) []string {
 	var name []string
 
@@ -122,3 +132,12 @@ func GetMailboxName(label proton.Label) []string {
 
 	return name
 }
+
+func nameWithTempPrefix(path []string) []string {
+	path[len(path)-1] = "tmp_" + path[len(path)-1]
+	return path
+}
+
+func getMailboxNameWithTempPrefix(label proton.Label) []string {
+	return nameWithTempPrefix(GetMailboxName(label))
+}

internal/services/imapservice/server_manager.go

@@ -21,6 +21,7 @@ import (
 	"context"
 
 	"github.com/ProtonMail/gluon/connector"
+	"github.com/ProtonMail/gluon/imap"
 	"github.com/ProtonMail/proton-bridge/v3/internal/services/syncservice"
 )
 
@@ -34,6 +35,10 @@ type IMAPServerManager interface {
 	) error
 
 	RemoveIMAPUser(ctx context.Context, deleteData bool, provider GluonIDProvider, addrID ...string) error
+
+	LogRemoteLabelIDs(ctx context.Context, provider GluonIDProvider, addrID ...string) error
+
+	GetUserMailboxByName(ctx context.Context, addrID string, mailboxName []string) (imap.MailboxData, error)
 }
 
 type NullIMAPServerManager struct{}
@@ -57,6 +62,18 @@ func (n NullIMAPServerManager) RemoveIMAPUser(
 	return nil
 }
 
+func (n NullIMAPServerManager) LogRemoteLabelIDs(
+	_ context.Context,
+	_ GluonIDProvider,
+	_ ...string,
+) error {
+	return nil
+}
+
+func (n NullIMAPServerManager) GetUserMailboxByName(_ context.Context, _ string, _ []string) (imap.MailboxData, error) {
+	return imap.MailboxData{}, nil
+}
+
 func NewNullIMAPServerManager() *NullIMAPServerManager {
 	return &NullIMAPServerManager{}
 }

internal/services/imapservice/service.go

@@ -36,6 +36,7 @@ import (
 	"github.com/ProtonMail/proton-bridge/v3/internal/services/syncservice"
 	"github.com/ProtonMail/proton-bridge/v3/internal/services/userevents"
 	"github.com/ProtonMail/proton-bridge/v3/internal/services/useridentity"
+	"github.com/ProtonMail/proton-bridge/v3/internal/unleash"
 	"github.com/ProtonMail/proton-bridge/v3/internal/usertypes"
 	"github.com/ProtonMail/proton-bridge/v3/pkg/cpc"
 	"github.com/sirupsen/logrus"
@@ -91,7 +92,8 @@ type Service struct {
 	lastHandledEventID string
 	isSyncing          atomic.Bool
 
-	observabilitySender observability.Sender
+	observabilitySender  observability.Sender
+	labelConflictManager *LabelConflictManager
 }
 
 func NewService(
@@ -112,6 +114,7 @@ func NewService(
 	maxSyncMemory uint64,
 	showAllMail bool,
 	observabilitySender observability.Sender,
+	getFeatureFlagValueFn unleash.GetFlagValueFn,
 ) *Service {
 	subscriberName := fmt.Sprintf("imap-%v", identityState.User.ID)
 
@@ -121,7 +124,8 @@ func NewService(
 	})
 	rwIdentity := newRWIdentity(identityState, bridgePassProvider, keyPassProvider)
 
-	syncUpdateApplier := NewSyncUpdateApplier()
+	labelConflictManager := NewLabelConflictManager(serverManager, gluonIDProvider, client, reporter, getFeatureFlagValueFn)
+	syncUpdateApplier := NewSyncUpdateApplier(labelConflictManager)
 	syncMessageBuilder := NewSyncMessageBuilder(rwIdentity)
 	syncReporter := newSyncReporter(identityState.User.ID, eventPublisher, time.Second)
 
@@ -156,7 +160,8 @@ func NewService(
 		syncReporter:       syncReporter,
 		syncConfigPath:     GetSyncConfigPath(syncConfigDir, identityState.User.ID),
 
-		observabilitySender: observabilitySender,
+		observabilitySender:  observabilitySender,
+		labelConflictManager: labelConflictManager,
 	}
 }
 
@@ -355,6 +360,12 @@ func (s *Service) run(ctx context.Context) { //nolint gocyclo
 
 			case *onBadEventReq:
 				s.log.Debug("Bad Event Request")
+				// // Log remote label IDs stored in the local labelMap.
+				s.labels.LogLabels()
+				// Log the remote label IDs store in Gluon.
+				if err := s.logRemoteMailboxIDsFromServer(ctx, s.connectors); err != nil {
+					s.log.Warnf("Could not obtain remote mailbox IDs from server: %v", err)
+				}
 				err := s.removeConnectorsFromServer(ctx, s.connectors, false)
 				req.Reply(ctx, nil, err)
 
@@ -572,6 +583,16 @@ func (s *Service) addConnectorsToServer(ctx context.Context, connectors map[stri
 	return nil
 }
 
+func (s *Service) logRemoteMailboxIDsFromServer(ctx context.Context, connectors map[string]*Connector) error {
+	addrIDs := make([]string, 0, len(connectors))
+
+	for _, c := range connectors {
+		addrIDs = append(addrIDs, c.addrID)
+	}
+
+	return s.serverManager.LogRemoteLabelIDs(ctx, s.gluonIDProvider, addrIDs...)
+}
+
 func (s *Service) removeConnectorsFromServer(ctx context.Context, connectors map[string]*Connector, deleteData bool) error {
 	addrIDs := make([]string, 0, len(connectors))
 

internal/services/imapservice/service_address_events.go

@@ -165,7 +165,7 @@ func addNewAddressSplitMode(ctx context.Context, s *Service, addrID string) erro
 
 	s.connectors[connector.addrID] = connector
 
-	updates, err := syncLabels(ctx, s.labels.GetLabelMap(), []*Connector{connector})
+	updates, err := syncLabels(ctx, s.labels.GetLabelMap(), []*Connector{connector}, s.labelConflictManager)
 	if err != nil {
 		return fmt.Errorf("failed to create labels updates for new address: %w", err)
 	}

internal/services/imapservice/service_label_events.go

@@ -42,7 +42,10 @@ func (s *Service) HandleLabelEvents(ctx context.Context, events []proton.LabelEv
 				continue
 			}
 
-			updates := onLabelCreated(ctx, s, event)
+			updates, err := onLabelCreated(ctx, s, event)
+			if err != nil {
+				return fmt.Errorf("failed to handle create label event: %w", err)
+			}
 
 			if err := waitOnIMAPUpdates(ctx, updates); err != nil {
 				return err
@@ -74,8 +77,8 @@ func (s *Service) HandleLabelEvents(ctx context.Context, events []proton.LabelEv
 	return nil
 }
 
-func onLabelCreated(ctx context.Context, s *Service, event proton.LabelEvent) []imap.Update {
-	updates := make([]imap.Update, 0, len(s.connectors))
+func onLabelCreated(ctx context.Context, s *Service, event proton.LabelEvent) ([]imap.Update, error) {
+	updates := []imap.Update{}
 
 	s.log.WithFields(logrus.Fields{
 		"labelID": event.ID,
@@ -85,9 +88,19 @@ func onLabelCreated(ctx context.Context, s *Service, event proton.LabelEvent) []
 	wr := s.labels.Write()
 	defer wr.Close()
 
-	wr.SetLabel(event.Label.ID, event.Label)
+	wr.SetLabel(event.Label.ID, event.Label, "onLabelCreated")
+
+	labelConflictResolver := s.labelConflictManager.NewConflictResolver(maps.Values(s.connectors))
+	conflictUpdatesGenerator, err := labelConflictResolver.ResolveConflict(ctx, event.Label, make(map[string]bool))
+	if err != nil {
+		return updates, err
+	}
 
 	for _, updateCh := range maps.Values(s.connectors) {
+		conflictUpdates := conflictUpdatesGenerator()
+		updateCh.publishUpdate(ctx, conflictUpdates...)
+		updates = append(updates, conflictUpdates...)
+
 		update := newMailboxCreatedUpdate(imap.MailboxID(event.ID), GetMailboxName(event.Label))
 		updateCh.publishUpdate(ctx, update)
 		updates = append(updates, update)
@@ -99,7 +112,7 @@ func onLabelCreated(ctx context.Context, s *Service, event proton.LabelEvent) []
 		Name:    event.Label.Name,
 	})
 
-	return updates
+	return updates, nil
 }
 
 func onLabelUpdated(ctx context.Context, s *Service, event proton.LabelEvent) ([]imap.Update, error) {
@@ -121,7 +134,7 @@ func onLabelUpdated(ctx context.Context, s *Service, event proton.LabelEvent) ([
 
 		// Only update the label if it exists; we don't want to create it as a client may have just deleted it.
 		if _, ok := wr.GetLabel(label.ID); ok {
-			wr.SetLabel(label.ID, event.Label)
+			wr.SetLabel(label.ID, event.Label, "onLabelUpdatedLabelEventID")
 		}
 
 		// API doesn't notify us that the path has changed. We need to fetch it again.
@@ -134,10 +147,21 @@ func onLabelUpdated(ctx context.Context, s *Service, event proton.LabelEvent) ([
 		}
 
 		// Update the label in the map.
-		wr.SetLabel(apiLabel.ID, apiLabel)
+		wr.SetLabel(apiLabel.ID, apiLabel, "onLabelUpdatedApiID")
+
+		// Resolve potential conflicts
+		labelConflictResolver := s.labelConflictManager.NewConflictResolver(maps.Values(s.connectors))
+		conflictUpdatesGenerator, err := labelConflictResolver.ResolveConflict(ctx, event.Label, make(map[string]bool))
+		if err != nil {
+			return updates, err
+		}
 
 		// Notify the IMAP clients.
 		for _, updateCh := range maps.Values(s.connectors) {
+			conflictUpdates := conflictUpdatesGenerator()
+			updateCh.publishUpdate(ctx, conflictUpdates...)
+			updates = append(updates, conflictUpdates...)
+
 			update := imap.NewMailboxUpdated(
 				imap.MailboxID(apiLabel.ID),
 				GetMailboxName(apiLabel),
@@ -176,7 +200,7 @@ func onLabelDeleted(ctx context.Context, s *Service, event proton.LabelEvent) []
 	wr := s.labels.Write()
 	wr.Close()
 
-	wr.Delete(event.ID)
+	wr.Delete(event.ID, "onLabelDeleted")
 
 	s.eventPublisher.PublishEvent(ctx, events.UserLabelDeleted{
 		UserID:  s.identityState.UserID(),

internal/services/imapservice/service_message_events.go

@@ -256,8 +256,8 @@ func onMessageUpdateDraftOrSent(ctx context.Context, s *Service, event proton.Me
 			res.update.Literal,
 			res.update.MailboxIDs,
 			res.update.ParsedMessage,
-			true, // Is the message doesn't exist, silently create it.
-			false,
+			true,       // Is the message doesn't exist, silently create it.
+			duringSync, // Ignore unknown labelIDs during sync.
 		)
 
 		didPublish, err := safePublishMessageUpdate(ctx, s, full.AddressID, update, duringSync)

internal/services/imapservice/service_sync_events.go

@@ -113,7 +113,7 @@ func (s syncMessageEventHandler) HandleMessageEvents(ctx context.Context, events
 			if err := waitOnIMAPUpdates(ctx, updates); gluon.IsNoSuchMessage(err) {
 				logrus.WithError(err).Error("Failed to handle update message event in gluon, will try creating it (sync)")
 
-				updates, err := onMessageCreated(ctx, s.service, event.Message, false, true)
+				updates, err := onMessageCreated(ctx, s.service, event.Message, true, true)
 				if err != nil {
 					s.service.observabilitySender.AddDistinctMetrics(
 						observability.SyncError,

internal/services/imapservice/shared_labels.go

@@ -22,6 +22,8 @@ import (
 
 	"github.com/ProtonMail/go-proton-api"
 	"github.com/ProtonMail/proton-bridge/v3/internal/usertypes"
+	"github.com/bradenaw/juniper/xslices"
+	"github.com/sirupsen/logrus"
 	"golang.org/x/exp/maps"
 )
 
@@ -42,8 +44,8 @@ type labelsRead interface {
 
 type labelsWrite interface {
 	labelsRead
-	SetLabel(id string, label proton.Label)
-	Delete(id string)
+	SetLabel(id string, label proton.Label, actionSource string)
+	Delete(id string, actionSource string)
 }
 
 type rwLabels struct {
@@ -51,6 +53,22 @@ type rwLabels struct {
 	labels labelMap
 }
 
+func (r *rwLabels) LogLabels() {
+	r.lock.RLock()
+	defer r.lock.RUnlock()
+
+	remoteLabelIDs := make([]string, len(r.labels))
+	i := 0
+	for labelID := range r.labels {
+		remoteLabelIDs[i] = labelID
+		i++
+	}
+
+	logrus.WithFields(logrus.Fields{
+		"remoteLabelIDs": remoteLabelIDs,
+	}).Debug("Logging remote label IDs stored in labelMap")
+}
+
 func (r *rwLabels) Read() labelsRead {
 	r.lock.RLock()
 	return &rwLabelsRead{rw: r}
@@ -75,6 +93,15 @@ func (r *rwLabels) SetLabels(labels []proton.Label) {
 	r.lock.Lock()
 	defer r.lock.Unlock()
 
+	labelIDs := xslices.Map(labels, func(label proton.Label) string {
+		return label.ID
+	})
+
+	logrus.WithFields(logrus.Fields{
+		"pkg":      "rwLabels",
+		"labelIDs": labelIDs,
+	}).Info("Setting labels")
+
 	r.labels = usertypes.GroupBy(labels, func(label proton.Label) string { return label.ID })
 }
 
@@ -123,10 +150,20 @@ func (r rwLabelsWrite) GetLabels() []proton.Label {
 	return r.rw.getLabelsUnsafe()
 }
 
-func (r rwLabelsWrite) SetLabel(id string, label proton.Label) {
+func (r rwLabelsWrite) SetLabel(id string, label proton.Label, actionSource string) {
+	logAction("SetLabel", actionSource, label.ID)
 	r.rw.labels[id] = label
 }
 
-func (r rwLabelsWrite) Delete(id string) {
+func (r rwLabelsWrite) Delete(id string, actionSource string) {
+	logAction("Delete", actionSource, id)
 	delete(r.rw.labels, id)
 }
+
+func logAction(actionType, actionSource, labelID string) {
+	logrus.WithFields(logrus.Fields{
+		"pkg":          "rwLabelsWrite",
+		"actionSource": actionSource,
+		"labelID":      labelID,
+	}).Debug(actionType)
+}

internal/services/imapservice/sync_update_applier.go

@@ -31,8 +31,9 @@ import (
 )
 
 type SyncUpdateApplier struct {
-	requestCh chan updateRequest
-	replyCh   chan updateReply
+	requestCh            chan updateRequest
+	replyCh              chan updateReply
+	labelConflictManager *LabelConflictManager
 }
 
 type updateReply struct {
@@ -42,10 +43,11 @@ type updateReply struct {
 
 type updateRequest = func(ctx context.Context, mode usertypes.AddressMode, connectors map[string]*Connector) ([]imap.Update, error)
 
-func NewSyncUpdateApplier() *SyncUpdateApplier {
+func NewSyncUpdateApplier(labelConflictManager *LabelConflictManager) *SyncUpdateApplier {
 	return &SyncUpdateApplier{
-		requestCh: make(chan updateRequest),
-		replyCh:   make(chan updateReply),
+		requestCh:            make(chan updateRequest),
+		replyCh:              make(chan updateReply),
+		labelConflictManager: labelConflictManager,
 	}
 }
 
@@ -111,42 +113,9 @@ func (s *SyncUpdateApplier) ApplySyncUpdates(ctx context.Context, updates []sync
 	return nil
 }
 
-func (s *SyncUpdateApplier) SyncSystemLabelsOnly(ctx context.Context, labels map[string]proton.Label) error {
-	request := func(ctx context.Context, _ usertypes.AddressMode, connectors map[string]*Connector) ([]imap.Update, error) {
-		updates := make([]imap.Update, 0, len(labels)*len(connectors))
-		for _, label := range labels {
-			if !WantLabel(label) {
-				continue
-			}
-
-			if label.Type != proton.LabelTypeSystem {
-				continue
-			}
-
-			for _, c := range connectors {
-				update := newSystemMailboxCreatedUpdate(imap.MailboxID(label.ID), label.Name)
-				updates = append(updates, update)
-				c.publishUpdate(ctx, update)
-			}
-		}
-		return updates, nil
-	}
-
-	updates, err := s.sendRequest(ctx, request)
-	if err != nil {
-		return err
-	}
-
-	if err := waitOnIMAPUpdates(ctx, updates); err != nil {
-		return fmt.Errorf("could not sync system labels: %w", err)
-	}
-
-	return nil
-}
-
 func (s *SyncUpdateApplier) SyncLabels(ctx context.Context, labels map[string]proton.Label) error {
 	request := func(ctx context.Context, _ usertypes.AddressMode, connectors map[string]*Connector) ([]imap.Update, error) {
-		return syncLabels(ctx, labels, maps.Values(connectors))
+		return syncLabels(ctx, labels, maps.Values(connectors), s.labelConflictManager)
 	}
 
 	updates, err := s.sendRequest(ctx, request)
@@ -161,9 +130,11 @@ func (s *SyncUpdateApplier) SyncLabels(ctx context.Context, labels map[string]pr
 }
 
 // nolint:exhaustive
-func syncLabels(ctx context.Context, labels map[string]proton.Label, connectors []*Connector) ([]imap.Update, error) {
+func syncLabels(ctx context.Context, labels map[string]proton.Label, connectors []*Connector, labelConflictManager *LabelConflictManager) ([]imap.Update, error) {
 	var updates []imap.Update
 
+	labelConflictResolver := labelConflictManager.NewConflictResolver(connectors)
+
 	// Create placeholder Folders/Labels mailboxes with the \Noselect attribute.
 	for _, prefix := range []string{folderPrefix, labelPrefix} {
 		for _, updateCh := range connectors {
@@ -188,7 +159,16 @@ func syncLabels(ctx context.Context, labels map[string]proton.Label, connectors
 			}
 
 		case proton.LabelTypeFolder, proton.LabelTypeLabel:
+			conflictUpdatesGenerator, err := labelConflictResolver.ResolveConflict(ctx, label, make(map[string]bool))
+			if err != nil {
+				return updates, err
+			}
+
 			for _, updateCh := range connectors {
+				conflictUpdates := conflictUpdatesGenerator()
+				updateCh.publishUpdate(ctx, conflictUpdates...)
+				updates = append(updates, conflictUpdates...)
+
 				update := newMailboxCreatedUpdate(imap.MailboxID(labelID), GetMailboxName(label))
 				updateCh.publishUpdate(ctx, update)
 				updates = append(updates, update)

internal/services/imapservice/utils.go

@@ -0,0 +1,100 @@
+// Copyright (c) 2025 Proton AG
+//
+// This file is part of Proton Mail Bridge.
+//
+// Proton Mail Bridge is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Proton Mail Bridge is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Proton Mail Bridge.  If not, see <https://www.gnu.org/licenses/>.
+
+package imapservice
+
+import (
+	"errors"
+
+	"github.com/ProtonMail/go-proton-api"
+	"github.com/ProtonMail/proton-bridge/v3/internal/usertypes"
+	"github.com/ProtonMail/proton-bridge/v3/pkg/message/parser"
+)
+
+type connectorInterface interface {
+	getSenderProtonAddress(p *parser.Parser) (proton.Address, error)
+	getAddress(id string) (proton.Address, bool)
+	getPrimaryAddress() (proton.Address, error)
+	getAddressMode() usertypes.AddressMode
+	logError(err error, errMsg string)
+}
+
+func (s *Connector) logError(err error, errMsg string) {
+	s.log.WithError(err).Warn(errMsg)
+}
+
+func (s *Connector) getAddressMode() usertypes.AddressMode {
+	return s.addressMode
+}
+
+func (s *Connector) getPrimaryAddress() (proton.Address, error) {
+	return s.identityState.GetPrimaryAddress()
+}
+
+func (s *Connector) getAddress(id string) (proton.Address, bool) {
+	return s.identityState.GetAddress(id)
+}
+
+func getImportAddress(p *parser.Parser, isDraft bool, id string, conn connectorInterface) (proton.Address, error) {
+	// addr is primary for combined mode or active for split mode
+	address, ok := conn.getAddress(id)
+	if !ok {
+		return proton.Address{}, errors.New("could not find account address")
+	}
+
+	// If the address is external and not BYOE - with sending enabled, then use the primary address as an import target.
+	if address.Type == proton.AddressTypeExternal && !address.Send {
+		var err error
+		address, err = conn.getPrimaryAddress()
+		if err != nil {
+			return proton.Address{}, errors.New("could not get primary account address")
+		}
+	}
+
+	inCombinedMode := conn.getAddressMode() == usertypes.AddressModeCombined
+	if !inCombinedMode {
+		return address, nil
+	}
+
+	senderAddr, err := conn.getSenderProtonAddress(p)
+	if err != nil {
+		if !errors.Is(err, errNoSenderAddressMatch) {
+			conn.logError(err, "Could not get import address")
+		}
+
+		// We did not find a match, so we use the default address.
+		return address, nil
+	}
+
+	if senderAddr.ID == address.ID {
+		return address, nil
+	}
+
+	// GODT-3185 / BRIDGE-120 In combined mode, in certain cases we adapt the address used for encryption.
+	// - draft with non-default address in combined mode: using sender address
+	// - import with non-default address in combined mode: using sender address
+	// - import with non-default disabled address in combined mode: using sender address
+	isSenderAddressDisabled := (!bool(senderAddr.Send)) || (senderAddr.Status != proton.AddressStatusEnabled)
+	isSenderExternalNonBYOE := senderAddr.Type == proton.AddressTypeExternal && !bool(senderAddr.Send)
+
+	// Forbid drafts/imports for external non-BYOE addresses
+	if isSenderExternalNonBYOE || (isDraft && isSenderAddressDisabled) {
+		return address, nil
+	}
+
+	return senderAddr, nil
+}

internal/services/imapservice/utils_test.go

@@ -0,0 +1,380 @@
+// Copyright (c) 2025 Proton AG
+//
+// This file is part of Proton Mail Bridge.
+//
+// Proton Mail Bridge is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Proton Mail Bridge is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Proton Mail Bridge.  If not, see <https://www.gnu.org/licenses/>.
+
+package imapservice
+
+import (
+	"errors"
+	"testing"
+
+	"github.com/ProtonMail/go-proton-api"
+	"github.com/ProtonMail/proton-bridge/v3/internal/usertypes"
+	"github.com/ProtonMail/proton-bridge/v3/pkg/message/parser"
+	"github.com/stretchr/testify/require"
+)
+
+type testConnector struct {
+	addressMode        usertypes.AddressMode
+	primaryAddress     proton.Address
+	senderAddress      proton.Address
+	imapAddress        proton.Address
+	senderAddressError error
+}
+
+func (t *testConnector) getSenderProtonAddress(_ *parser.Parser) (proton.Address, error) {
+	return t.senderAddress, t.senderAddressError
+}
+
+func (t *testConnector) getAddress(_ string) (proton.Address, bool) {
+	return t.imapAddress, true
+}
+
+func (t *testConnector) getPrimaryAddress() (proton.Address, error) {
+	return t.primaryAddress, nil
+}
+
+func (t *testConnector) getAddressMode() usertypes.AddressMode {
+	return t.addressMode
+}
+
+func (t *testConnector) logError(_ error, _ string) {
+}
+
+func Test_GetImportAddress_SplitMode(t *testing.T) {
+	primaryAddress := proton.Address{
+		ID:      "1",
+		Email:   "primary@proton.me",
+		Send:    true,
+		Receive: true,
+		Type:    proton.AddressTypeOriginal,
+		Status:  proton.AddressStatusEnabled,
+	}
+
+	imapAddressProton := proton.Address{
+		ID:      "2",
+		Email:   "imap@proton.me",
+		Send:    true,
+		Receive: true,
+		Type:    proton.AddressTypeOriginal,
+	}
+
+	testConn := &testConnector{
+		addressMode:    usertypes.AddressModeSplit,
+		primaryAddress: primaryAddress,
+		imapAddress:    imapAddressProton,
+	}
+
+	// Import address is internal, we're creating a draft.
+	// Expected: returned address is internal.
+	addr, err := getImportAddress(nil, true, imapAddressProton.ID, testConn)
+	require.NoError(t, err)
+	require.Equal(t, imapAddressProton.ID, addr.ID)
+	require.Equal(t, imapAddressProton.Email, addr.Email)
+
+	// Import address is internal, we're attempting to import a message.
+	// Expected: returned address is internal.
+	addr, err = getImportAddress(nil, false, imapAddressProton.ID, testConn)
+	require.NoError(t, err)
+	require.Equal(t, imapAddressProton.ID, addr.ID)
+	require.Equal(t, imapAddressProton.Email, addr.Email)
+
+	imapAddressBYOE := proton.Address{
+		ID:      "3",
+		Email:   "byoe@external.com",
+		Send:    true,
+		Receive: true,
+		Type:    proton.AddressTypeExternal,
+	}
+
+	// IMAP address is BYOE, we're creating a draft
+	// Expected: returned address is BYOE.
+	testConn.imapAddress = imapAddressBYOE
+	addr, err = getImportAddress(nil, true, imapAddressBYOE.ID, testConn)
+	require.NoError(t, err)
+	require.Equal(t, imapAddressBYOE.ID, addr.ID)
+	require.Equal(t, imapAddressBYOE.Email, addr.Email)
+	// IMAP address is BYOE, we're importing a message
+	// Expected: returned address is BYOE.
+	addr, err = getImportAddress(nil, false, imapAddressBYOE.ID, testConn)
+	require.NoError(t, err)
+	require.Equal(t, imapAddressBYOE.ID, addr.ID)
+	require.Equal(t, imapAddressBYOE.Email, addr.Email)
+
+	imapAddressExternal := proton.Address{
+		ID:      "4",
+		Email:   "external@external.com",
+		Send:    false,
+		Receive: false,
+		Type:    proton.AddressTypeExternal,
+	}
+
+	// IMAP address is external, we're creating a draft.
+	// Expected: returned address is primary.
+	testConn.imapAddress = imapAddressExternal
+	addr, err = getImportAddress(nil, true, imapAddressExternal.ID, testConn)
+	require.NoError(t, err)
+	require.Equal(t, primaryAddress.ID, addr.ID)
+	require.Equal(t, primaryAddress.Email, addr.Email)
+	// IMAP address is external, we're trying to import.
+	// Expected: returned address is primary.
+	addr, err = getImportAddress(nil, false, imapAddressExternal.ID, testConn)
+	require.NoError(t, err)
+	require.Equal(t, primaryAddress.ID, addr.ID)
+	require.Equal(t, primaryAddress.Email, addr.Email)
+}
+
+func Test_GetImportAddress_CombinedMode_ProtonAddresses(t *testing.T) {
+	primaryAddress := proton.Address{
+		ID:      "1",
+		Email:   "primary@proton.me",
+		Send:    true,
+		Receive: true,
+		Type:    proton.AddressTypeOriginal,
+		Status:  proton.AddressStatusEnabled,
+	}
+
+	imapAddressProton := proton.Address{
+		ID:      "2",
+		Email:   "imap@proton.me",
+		Send:    true,
+		Receive: true,
+		Type:    proton.AddressTypeOriginal,
+	}
+
+	senderAddress := proton.Address{
+		ID:      "3",
+		Email:   "sender@proton.me",
+		Send:    true,
+		Receive: true,
+		Type:    proton.AddressTypeOriginal,
+		Status:  proton.AddressStatusEnabled,
+	}
+
+	testConn := &testConnector{
+		addressMode:    usertypes.AddressModeCombined,
+		primaryAddress: primaryAddress,
+		imapAddress:    imapAddressProton,
+		senderAddress:  senderAddress,
+	}
+
+	// Both the sender address and the imap address are the same. We're creating a draft.
+	// Expected: IMAP address is returned.
+	testConn.senderAddress = imapAddressProton
+	testConn.imapAddress = imapAddressProton
+	addr, err := getImportAddress(nil, true, imapAddressProton.ID, testConn)
+	require.NoError(t, err)
+	require.Equal(t, imapAddressProton.ID, addr.ID)
+	require.Equal(t, imapAddressProton.Email, addr.Email)
+	// Both the sender address and the imap address are the same. We're trying to import
+	// Expected: IMAP address is returned.
+	addr, err = getImportAddress(nil, false, imapAddressProton.ID, testConn)
+	require.NoError(t, err)
+	require.Equal(t, imapAddressProton.ID, addr.ID)
+	require.Equal(t, imapAddressProton.Email, addr.Email)
+
+	// Sender address and imap address are different. Sender address is enabled and has sending enabled.
+	// We're creating a draft.
+	// Expected: Sender address is returned.
+	testConn.senderAddress = senderAddress
+	testConn.imapAddress = imapAddressProton
+	addr, err = getImportAddress(nil, true, imapAddressProton.ID, testConn)
+	require.NoError(t, err)
+	require.Equal(t, senderAddress.ID, addr.ID)
+	require.Equal(t, senderAddress.Email, addr.Email)
+	// Sender address and imap address are different. Sender address is enabled and has sending enabled.
+	// We're importing a message.
+	// Expected: Sender address is returned.
+	addr, err = getImportAddress(nil, false, imapAddressProton.ID, testConn)
+	require.NoError(t, err)
+	require.Equal(t, senderAddress.ID, addr.ID)
+	require.Equal(t, senderAddress.Email, addr.Email)
+
+	// Sender address and imap address are different. Sender address is disabled, but has sending enabled.
+	// We're creating a draft message.
+	// Expected: IMAP address is returned.
+	senderAddress.Status = proton.AddressStatusDisabled
+	testConn.senderAddress = senderAddress
+	addr, err = getImportAddress(nil, true, imapAddressProton.ID, testConn)
+	require.NoError(t, err)
+	require.Equal(t, imapAddressProton.ID, addr.ID)
+	require.Equal(t, imapAddressProton.Email, addr.Email)
+	// Sender address and imap address are different. Sender address is disabled, but has sending enabled.
+	// We're importing a message.
+	// Expected: IMAP address is returned.
+	addr, err = getImportAddress(nil, false, imapAddressProton.ID, testConn)
+	require.NoError(t, err)
+	require.Equal(t, senderAddress.ID, addr.ID)
+	require.Equal(t, senderAddress.Email, addr.Email)
+
+	// Sender address and imap address are different. Sender address is enabled, but has sending disabled.
+	// We're creating a draft.
+	// Expected: IMAP address is returned.
+	senderAddress.Status = proton.AddressStatusEnabled
+	senderAddress.Send = false
+	testConn.senderAddress = senderAddress
+	addr, err = getImportAddress(nil, true, imapAddressProton.ID, testConn)
+	require.NoError(t, err)
+	require.Equal(t, imapAddressProton.ID, addr.ID)
+	require.Equal(t, imapAddressProton.Email, addr.Email)
+	// Sender address and imap address are different. Sender address is enabled, but has sending disabled.
+	// We're importing a message.
+	// Expected: IMAP address is returned.
+	addr, err = getImportAddress(nil, false, imapAddressProton.ID, testConn)
+	require.NoError(t, err)
+	require.Equal(t, senderAddress.ID, addr.ID)
+	require.Equal(t, senderAddress.Email, addr.Email)
+
+	// Sender address and imap address are different. But sender address is not an associated proton address.
+	// We're creating a draft.
+	// Expected: Sender address is returned.
+	testConn.senderAddressError = errors.New("sender address is not associated with the account")
+	addr, err = getImportAddress(nil, true, imapAddressProton.ID, testConn)
+	require.NoError(t, err)
+	require.Equal(t, imapAddressProton.ID, addr.ID)
+	require.Equal(t, imapAddressProton.Email, addr.Email)
+	// Sender address and imap address are different. But sender address is not an associated proton address.
+	// We're importing a message.
+	// Expected: Sender address is returned.
+	addr, err = getImportAddress(nil, false, imapAddressProton.ID, testConn)
+	require.NoError(t, err)
+	require.Equal(t, imapAddressProton.ID, addr.ID)
+	require.Equal(t, imapAddressProton.Email, addr.Email)
+}
+
+func Test_GetImportAddress_CombinedMode_ExternalAddresses(t *testing.T) {
+	primaryAddress := proton.Address{
+		ID:      "1",
+		Email:   "primary@proton.me",
+		Send:    true,
+		Receive: true,
+		Type:    proton.AddressTypeOriginal,
+		Status:  proton.AddressStatusEnabled,
+	}
+
+	imapAddressProton := proton.Address{
+		ID:      "2",
+		Email:   "imap@proton.me",
+		Send:    true,
+		Receive: true,
+		Type:    proton.AddressTypeOriginal,
+	}
+
+	senderAddressExternal := proton.Address{
+		ID:      "3",
+		Email:   "sender@external.me",
+		Send:    false,
+		Receive: false,
+		Type:    proton.AddressTypeExternal,
+		Status:  proton.AddressStatusEnabled,
+	}
+
+	senderAddressExternalSecondary := proton.Address{
+		ID:      "4",
+		Email:   "sender2@external.me",
+		Send:    false,
+		Receive: false,
+		Type:    proton.AddressTypeExternal,
+		Status:  proton.AddressStatusEnabled,
+	}
+
+	testConn := &testConnector{
+		addressMode:    usertypes.AddressModeCombined,
+		primaryAddress: primaryAddress,
+		imapAddress:    imapAddressProton,
+		senderAddress:  senderAddressExternal,
+	}
+
+	// Sender address is external, and we're creating a draft.
+	// Expected: IMAP address is returned.
+	testConn.senderAddress = senderAddressExternal
+	testConn.imapAddress = imapAddressProton
+	addr, err := getImportAddress(nil, true, imapAddressProton.ID, testConn)
+	require.NoError(t, err)
+	require.Equal(t, imapAddressProton.ID, addr.ID)
+	require.Equal(t, imapAddressProton.Email, addr.Email)
+	// Sender address is external, and we're importing a message.
+	// Expected: IMAP address is returned.
+	addr, err = getImportAddress(nil, false, imapAddressProton.ID, testConn)
+	require.NoError(t, err)
+	require.Equal(t, imapAddressProton.ID, addr.ID)
+	require.Equal(t, imapAddressProton.Email, addr.Email)
+
+	// Sender and IMAP address are external, and we're trying to import.
+	// Expected: Primary address is returned.
+	testConn.imapAddress = senderAddressExternalSecondary
+	addr, err = getImportAddress(nil, false, imapAddressProton.ID, testConn)
+	require.NoError(t, err)
+	require.Equal(t, primaryAddress.ID, addr.ID)
+	require.Equal(t, primaryAddress.Email, addr.Email)
+	// Sender and IMAP address are external, and we're trying to create a draft.
+	// Expected: Primary address is returned.
+	addr, err = getImportAddress(nil, true, imapAddressProton.ID, testConn)
+	require.NoError(t, err)
+	require.Equal(t, primaryAddress.ID, addr.ID)
+	require.Equal(t, primaryAddress.Email, addr.Email)
+}
+
+func Test_GetImportAddress_CombinedMode_BYOEAddresses(t *testing.T) {
+	primaryAddress := proton.Address{
+		ID:      "1",
+		Email:   "primary@proton.me",
+		Send:    true,
+		Receive: true,
+		Type:    proton.AddressTypeOriginal,
+		Status:  proton.AddressStatusEnabled,
+	}
+
+	imapAddressProton := proton.Address{
+		ID:      "2",
+		Email:   "imap@proton.me",
+		Send:    true,
+		Receive: true,
+		Type:    proton.AddressTypeOriginal,
+	}
+
+	senderAddressBYOE := proton.Address{
+		ID:      "3",
+		Email:   "sender@external.me",
+		Send:    true,
+		Receive: true,
+		Type:    proton.AddressTypeExternal,
+		Status:  proton.AddressStatusEnabled,
+	}
+
+	testConn := &testConnector{
+		addressMode:    usertypes.AddressModeCombined,
+		primaryAddress: primaryAddress,
+		imapAddress:    imapAddressProton,
+		senderAddress:  senderAddressBYOE,
+	}
+
+	// Sender address is BYOE, and we're creating a draft.
+	// Expected: BYOE address is returned.
+	testConn.senderAddress = senderAddressBYOE
+	testConn.imapAddress = imapAddressProton
+	addr, err := getImportAddress(nil, true, imapAddressProton.ID, testConn)
+	require.NoError(t, err)
+	require.Equal(t, senderAddressBYOE.ID, addr.ID)
+	require.Equal(t, senderAddressBYOE.Email, addr.Email)
+
+	// Sender address is BYOE, and we're importing a message.
+	// Expected: BYOE address is returned.
+	addr, err = getImportAddress(nil, false, imapAddressProton.ID, testConn)
+	require.NoError(t, err)
+	require.Equal(t, senderAddressBYOE.ID, addr.ID)
+	require.Equal(t, senderAddressBYOE.Email, addr.Email)
+}

internal/services/imapsmtpserver/service.go

@@ -170,6 +170,14 @@ func (sm *Service) SetGluonDir(ctx context.Context, gluonDir string) error {
 	return err
 }
 
+func (sm *Service) LogRemoteLabelIDs(ctx context.Context, provider imapservice.GluonIDProvider, addrID ...string) error {
+	_, err := sm.requests.Send(ctx, &smRequestLogRemoteMailboxIDs{
+		addrID:     addrID,
+		idProvider: provider,
+	})
+	return err
+}
+
 func (sm *Service) RemoveIMAPUser(ctx context.Context, deleteData bool, provider imapservice.GluonIDProvider, addrID ...string) error {
 	_, err := sm.requests.Send(ctx, &smRequestRemoveIMAPUser{
 		withData:   deleteData,
@@ -192,6 +200,10 @@ func (sm *Service) RemoveSMTPAccount(ctx context.Context, service *bridgesmtp.Se
 	return err
 }
 
+func (sm *Service) GetUserMailboxByName(ctx context.Context, addrID string, mailboxName []string) (imap.MailboxData, error) {
+	return sm.imapServer.GetUserMailboxByName(ctx, addrID, mailboxName)
+}
+
 func (sm *Service) run(ctx context.Context, subscription events.Subscription) {
 	eventSub := subscription.Add()
 	defer subscription.Remove(eventSub)
@@ -244,6 +256,10 @@ func (sm *Service) run(ctx context.Context, subscription events.Subscription) {
 					sm.handleLoadedUserCountChange(ctx)
 				}
 
+			case *smRequestLogRemoteMailboxIDs:
+				err := sm.logRemoteLabelIDsFromServer(ctx, r.addrID, r.idProvider)
+				request.Reply(ctx, nil, err)
+
 			case *smRequestRemoveIMAPUser:
 				err := sm.handleRemoveIMAPUser(ctx, r.withData, r.idProvider, r.addrID...)
 				request.Reply(ctx, nil, err)
@@ -311,6 +327,35 @@ func (sm *Service) handleAddIMAPUser(ctx context.Context,
 	return sm.handleAddIMAPUserImpl(ctx, connector, addrID, idProvider, syncStateProvider)
 }
 
+func (sm *Service) logRemoteLabelIDsFromServer(ctx context.Context, addrIDs []string, idProvider imapservice.GluonIDProvider) error {
+	if sm.imapServer == nil {
+		return fmt.Errorf("no imap server instance running")
+	}
+
+	for _, addrID := range addrIDs {
+		gluonID, ok := idProvider.GetGluonID(addrID)
+		if !ok {
+			sm.log.Warnf("Could not find Gluon ID for addrID %v", addrID)
+			continue
+		}
+
+		log := sm.log.WithFields(logrus.Fields{
+			"addrID":  addrID,
+			"gluonID": gluonID,
+		})
+
+		remoteLabelIDs, err := sm.imapServer.GetAllMailboxRemoteIDsForUser(ctx, gluonID)
+		if err != nil {
+			log.WithError(err).Error("Could not obtain remote label IDs for user")
+			continue
+		}
+
+		log.WithField("remoteLabelIDs", remoteLabelIDs).Debug("Logging Gluon remote Label IDs")
+	}
+
+	return nil
+}
+
 func (sm *Service) handleAddIMAPUserImpl(ctx context.Context,
 	connector connector.Connector,
 	addrID string,
@@ -723,3 +768,8 @@ type smRequestAddSMTPAccount struct {
 type smRequestRemoveSMTPAccount struct {
 	account *bridgesmtp.Service
 }
+
+type smRequestLogRemoteMailboxIDs struct {
+	addrID     []string
+	idProvider imapservice.GluonIDProvider
+}

internal/services/syncservice/handler.go

@@ -138,11 +138,10 @@ func (t *Handler) run(ctx context.Context,
 	}
 
 	if syncStatus.IsComplete() {
-		t.log.Info("Sync already complete, only system labels will be updated")
-
-		if err := updateApplier.SyncSystemLabelsOnly(ctx, labels); err != nil {
-			t.log.WithError(err).Error("Failed to sync system labels")
+		t.log.Info("Sync already complete, updating labels")
 
+		if err := updateApplier.SyncLabels(ctx, labels); err != nil {
+			t.log.WithError(err).Error("Failed to sync labels")
 			return err
 		}
 

internal/services/syncservice/handler_test.go

@@ -74,8 +74,7 @@ func TestTask_NoStateAndSucceeds(t *testing.T) {
 	}
 
 	{
-		call1 := tt.updateApplier.EXPECT().SyncLabels(gomock.Any(), gomock.Eq(labels)).Times(1).Return(nil)
-		tt.updateApplier.EXPECT().SyncSystemLabelsOnly(gomock.Any(), gomock.Eq(labels)).After(call1).Times(1).Return(nil)
+		tt.updateApplier.EXPECT().SyncLabels(gomock.Any(), gomock.Eq(labels)).Times(2).Return(nil)
 	}
 
 	{
@@ -203,7 +202,7 @@ func TestTask_StateHasSyncedState(t *testing.T) {
 		}, nil
 	})
 
-	tt.updateApplier.EXPECT().SyncSystemLabelsOnly(gomock.Any(), gomock.Eq(labels)).Return(nil)
+	tt.updateApplier.EXPECT().SyncLabels(gomock.Any(), gomock.Eq(labels)).Return(nil)
 
 	err := tt.task.run(context.Background(), tt.syncReporter, labels, tt.updateApplier, tt.messageBuilder)
 	require.NoError(t, err)

internal/services/syncservice/interfaces.go

@@ -80,7 +80,6 @@ type MessageBuilder interface {
 
 type UpdateApplier interface {
 	ApplySyncUpdates(ctx context.Context, updates []BuildResult) error
-	SyncSystemLabelsOnly(ctx context.Context, labels map[string]proton.Label) error
 	SyncLabels(ctx context.Context, labels map[string]proton.Label) error
 }
 

internal/services/syncservice/mocks_test.go

@@ -548,20 +548,6 @@ func (mr *MockUpdateApplierMockRecorder) SyncLabels(arg0, arg1 interface{}) *gom
 	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "SyncLabels", reflect.TypeOf((*MockUpdateApplier)(nil).SyncLabels), arg0, arg1)
 }
 
-// SyncSystemLabelsOnly mocks base method.
-func (m *MockUpdateApplier) SyncSystemLabelsOnly(arg0 context.Context, arg1 map[string]proton.Label) error {
-	m.ctrl.T.Helper()
-	ret := m.ctrl.Call(m, "SyncSystemLabelsOnly", arg0, arg1)
-	ret0, _ := ret[0].(error)
-	return ret0
-}
-
-// SyncSystemLabelsOnly indicates an expected call of SyncSystemLabelsOnly.
-func (mr *MockUpdateApplierMockRecorder) SyncSystemLabelsOnly(arg0, arg1 interface{}) *gomock.Call {
-	mr.mock.ctrl.T.Helper()
-	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "SyncSystemLabelsOnly", reflect.TypeOf((*MockUpdateApplier)(nil).SyncSystemLabelsOnly), arg0, arg1)
-}
-
 // MockMessageBuilder is a mock of MessageBuilder interface.
 type MockMessageBuilder struct {
 	ctrl     *gomock.Controller

internal/unleash/service.go

@@ -41,6 +41,7 @@ const (
 	IMAPAuthenticateCommandDisabled          = "InboxBridgeImapAuthenticateCommandDisabled"
 	UserRemovalGluonDataCleanupDisabled      = "InboxBridgeUserRemovalGluonDataCleanupDisabled"
 	UpdateUseNewVersionFileStructureDisabled = "InboxBridgeUpdateWithOsFilterDisabled"
+	LabelConflictResolverDisabled            = "InboxBridgeLabelConflictResolverDisabled"
 )
 
 type requestFeaturesFn func(ctx context.Context) (proton.FeatureFlagResult, error)

internal/user/user.go

@@ -282,6 +282,7 @@ func newImpl(
 		user.maxSyncMemory,
 		showAllMail,
 		observabilityService,
+		getFlagValueFn,
 	)
 
 	user.notificationService = notifications.NewService(user.id, user.eventService, user, notificationStore, getFlagValueFn, observabilityService)
@@ -739,7 +740,7 @@ func (user *User) protonAddresses() []proton.Address {
 	}
 
 	addresses := xslices.Filter(maps.Values(apiAddrs), func(addr proton.Address) bool {
-		return addr.Status == proton.AddressStatusEnabled && addr.Type != proton.AddressTypeExternal
+		return addr.Status == proton.AddressStatusEnabled && (addr.IsBYOEAddress() || addr.Type != proton.AddressTypeExternal)
 	})
 
 	slices.SortFunc(addresses, func(a, b proton.Address) bool {

internal/user/user_test.go

@@ -110,7 +110,7 @@ func withAccount(tb testing.TB, s *server.Server, username, password string, ali
 	addrIDs := []string{addrID}
 
 	for _, email := range aliases {
-		addrID, err := s.CreateAddress(userID, email, []byte(password))
+		addrID, err := s.CreateAddress(userID, email, []byte(password), true)
 		require.NoError(tb, err)
 		require.NoError(tb, s.ChangeAddressDisplayName(userID, addrID, email+" (Display Name)"))
 

internal/vault/helper.go

@@ -63,6 +63,10 @@ func GetHelper(vaultDir string) (string, error) {
 }
 
 func SetHelper(vaultDir, helper string) error {
+	if helper == "" {
+		return nil
+	}
+
 	settings, err := LoadKeychainSettings(vaultDir)
 	if err != nil {
 		return err

pkg/keychain/keychain.go

@@ -82,11 +82,11 @@ func (kcl *List) GetDefaultHelper() string {
 	return kcl.defaultHelper
 }
 
-// NewKeychain creates a new native keychain.
-func NewKeychain(preferred, keychainName string, helpers Helpers, defaultHelper string) (*Keychain, error) {
+// NewKeychain creates a new native keychain. It also returns the keychain helper used to access the keychain.
+func NewKeychain(preferred, keychainName string, helpers Helpers, defaultHelper string) (kc *Keychain, usedKeychainHelper string, err error) {
 	// There must be at least one keychain helper available.
 	if len(helpers) < 1 {
-		return nil, ErrNoKeychain
+		return nil, "", ErrNoKeychain
 	}
 
 	// If the preferred keychain is unsupported, fallback to the default one.
@@ -97,16 +97,16 @@ func NewKeychain(preferred, keychainName string, helpers Helpers, defaultHelper
 	// Load the user's preferred keychain helper.
 	helperConstructor, ok := helpers[preferred]
 	if !ok {
-		return nil, ErrNoKeychain
+		return nil, "", ErrNoKeychain
 	}
 
 	// Construct the keychain helper.
 	helper, err := helperConstructor(hostURL(keychainName))
 	if err != nil {
-		return nil, err
+		return nil, preferred, err
 	}
 
-	return newKeychain(helper, hostURL(keychainName)), nil
+	return newKeychain(helper, hostURL(keychainName)), preferred, nil
 }
 
 func newKeychain(helper credentials.Helper, url string) *Keychain {

pkg/keychain/keychain_test.go

@@ -120,7 +120,7 @@ func TestIsErrKeychainNoItem(t *testing.T) {
 	helpers := NewList().GetHelpers()
 
 	for helperName := range helpers {
-		kc, err := NewKeychain(helperName, "bridge-test", helpers, helperName)
+		kc, _, err := NewKeychain(helperName, "bridge-test", helpers, helperName)
 		r.NoError(err)
 
 		_, _, err = kc.Get("non-existing")

utils/govulncheck.sh

@@ -28,9 +28,7 @@ main(){
     jq -r '.finding | select( (.osv != null) and (.trace[0].function != null) ) | .osv ' < vulns.json > vulns_osv_ids.txt
 
     ignore GO-2023-2328 "GODT-3124 RESTY race condition"
-    ignore GO-2025-3373 "BRIDGE-315 stdlib crypto/x509"
-    ignore GO-2025-3420 "BRIDGE-315 stdlib net/http"
-    ignore GO-2025-3447 "BRIDGE-315 stdlib crypto/internal/nistec"
+    ignore GO-2025-3563 "BRIDGE-346 net/http request smuggling"
 
     has_vulns