diff --git a/Changelog.md b/Changelog.md
index 0d3e669b..3fdbddda 100644
--- a/Changelog.md
+++ b/Changelog.md
@@ -8,6 +8,7 @@ Changelog [format](http://keepachangelog.com/en/1.0.0/)
 
 ### Fixed
 * GODT-798 Replace, don't add, transfer encoding when making body 7-bit clean.
+* Move/Copy duplicate for emails with References in Outlook
 
 
 ## [Bridge 1.4.3] Forth
diff --git a/internal/imap/mailbox_message.go b/internal/imap/mailbox_message.go
index 5d25a2ae..5ae84d9c 100644
--- a/internal/imap/mailbox_message.go
+++ b/internal/imap/mailbox_message.go
@@ -24,7 +24,6 @@ import (
 	"mime/multipart"
 	"net/mail"
 	"net/textproto"
-	"regexp"
 	"sort"
 	"strings"
 	"time"
@@ -141,18 +140,19 @@ func (im *imapMailbox) CreateMessage(flags []string, date time.Time, body imap.L
 	references := m.Header.Get("References")
 	referenceList := strings.Fields(references)
 
-	if len(referenceList) > 0 {
+	// In case there is a mail client which corrupts headers, try
+	// "References" too.
+	if internalID == "" && len(referenceList) > 0 {
 		lastReference := referenceList[len(referenceList)-1]
-		// In case we are using a mail client which corrupts headers, try "References" too.
-		re := regexp.MustCompile(pmapi.InternalReferenceFormat)
-		match := re.FindStringSubmatch(lastReference)
-		if len(match) > 0 {
-			internalID = match[0]
+		match := pmapi.RxInternalReferenceFormat.FindStringSubmatch(lastReference)
+		if len(match) == 2 {
+			internalID = match[1]
 		}
 	}
 
-	// Avoid appending a message which is already on the server. Apply the new
-	// label instead. This sometimes happens which Outlook (it uses APPEND instead of COPY).
+	// Avoid appending a message which is already on the server. Apply the
+	// new label instead. This always happens with Outlook (it uses APPEND
+	// instead of COPY).
 	if internalID != "" {
 		// Check to see if this belongs to a different address in split mode or another ProtonMail account.
 		msg, err := im.storeMailbox.GetMessage(internalID)
diff --git a/internal/smtp/user.go b/internal/smtp/user.go
index 079c920f..37957249 100644
--- a/internal/smtp/user.go
+++ b/internal/smtp/user.go
@@ -25,7 +25,6 @@ import (
 	"io"
 	"mime"
 	"net/mail"
-	"regexp"
 	"strings"
 	"time"
 
@@ -408,9 +407,9 @@ func (su *smtpUser) handleReferencesHeader(m *pmapi.Message) (draftID, parentID
 		if !strings.Contains(reference, "@"+pmapi.InternalIDDomain) {
 			newReferences = append(newReferences, reference)
 		} else { // internalid is the parentID.
-			idMatch := regexp.MustCompile(pmapi.InternalReferenceFormat).FindStringSubmatch(reference)
-			if len(idMatch) > 0 {
-				lastID := strings.TrimSuffix(strings.Trim(idMatch[0], "<>"), "@protonmail.internalid")
+			idMatch := pmapi.RxInternalReferenceFormat.FindStringSubmatch(reference)
+			if len(idMatch) == 2 {
+				lastID := idMatch[1]
 				filter := &pmapi.MessagesFilter{ID: []string{lastID}}
 				if su.addressID != "" {
 					filter.AddressID = su.addressID
diff --git a/pkg/pmapi/messages.go b/pkg/pmapi/messages.go
index ed5d38b5..623bd07b 100644
--- a/pkg/pmapi/messages.go
+++ b/pkg/pmapi/messages.go
@@ -29,6 +29,7 @@ import (
 	"net/http"
 	"net/mail"
 	"net/url"
+	"regexp"
 	"strconv"
 	"strings"
 
@@ -149,8 +150,9 @@ const ConversationIDDomain = `protonmail.conversationid`
 // InternalIDDomain is used as a placeholder for reference/message ID headers to improve compatibility with various clients.
 const InternalIDDomain = `protonmail.internalid`
 
-// InternalReferenceFormat describes format of the message ID (as regex) used for parsing reference headers.
-const InternalReferenceFormat = `(?U)<.*@` + InternalIDDomain + `>`
+// RxInternalReferenceFormat is compiled regexp which describes the match for
+// a message ID used in reference headers.
+var RxInternalReferenceFormat = regexp.MustCompile(`(?U)<(.+)@` + regexp.QuoteMeta(InternalIDDomain) + `>`) //nolint[gochecknoglobals]
 
 // Message structure.
 type Message struct {