diff --git a/internal/bridge/imap.go b/internal/bridge/imap.go
index ef7872ac..97eed175 100644
--- a/internal/bridge/imap.go
+++ b/internal/bridge/imap.go
@@ -50,16 +50,6 @@ func (bridge *Bridge) addIMAPUser(ctx context.Context, user *user.User) error {
 	return bridge.serverManager.AddIMAPUser(ctx, user)
 }
 
-// addSMTPUser connects the given user to gluon.
-func (bridge *Bridge) addSMTPUser(ctx context.Context, user *user.User) error {
-	return bridge.serverManager.AddSMTPAccount(ctx, user.GetSMTPService())
-}
-
-// removeSMTPUser connects the given user to gluon.
-func (bridge *Bridge) removeSMTPUser(ctx context.Context, user *user.User) error {
-	return bridge.serverManager.RemoveSMTPAccount(ctx, user.GetSMTPService())
-}
-
 // removeIMAPUser disconnects the given user from gluon, optionally also removing its files.
 func (bridge *Bridge) removeIMAPUser(ctx context.Context, user *user.User, withData bool) error {
 	return bridge.serverManager.RemoveIMAPUser(ctx, user, withData)
diff --git a/internal/bridge/smtp.go b/internal/bridge/smtp.go
index 8645eb28..7939f11a 100644
--- a/internal/bridge/smtp.go
+++ b/internal/bridge/smtp.go
@@ -23,7 +23,8 @@ import (
 
 	"github.com/ProtonMail/proton-bridge/v3/internal/constants"
 	"github.com/ProtonMail/proton-bridge/v3/internal/logging"
-	bridgesmtp "github.com/ProtonMail/proton-bridge/v3/internal/services/smtp"
+	smtpservice "github.com/ProtonMail/proton-bridge/v3/internal/services/smtp"
+	"github.com/ProtonMail/proton-bridge/v3/internal/user"
 	"github.com/emersion/go-sasl"
 	"github.com/emersion/go-smtp"
 	"github.com/sirupsen/logrus"
@@ -33,10 +34,10 @@ func (bridge *Bridge) restartSMTP(ctx context.Context) error {
 	return bridge.serverManager.RestartSMTP(ctx)
 }
 
-func newSMTPServer(bridge *Bridge, accounts *bridgesmtp.Accounts, tlsConfig *tls.Config, logSMTP bool) *smtp.Server {
+func newSMTPServer(bridge *Bridge, accounts *smtpservice.Accounts, tlsConfig *tls.Config, logSMTP bool) *smtp.Server {
 	logrus.WithField("logSMTP", logSMTP).Info("Creating SMTP server")
 
-	smtpServer := smtp.NewServer(&smtpBackend{userAgent: &bridgeUserAgentUpdater{Bridge: bridge}, accounts: accounts})
+	smtpServer := smtp.NewServer(smtpservice.NewBackend(accounts, &bridgeUserAgentUpdater{Bridge: bridge}))
 
 	smtpServer.TLSConfig = tlsConfig
 	smtpServer.Domain = constants.Host
@@ -62,3 +63,13 @@ func newSMTPServer(bridge *Bridge, accounts *bridgesmtp.Accounts, tlsConfig *tls
 
 	return smtpServer
 }
+
+// addSMTPUser connects the given user to the smtp server.
+func (bridge *Bridge) addSMTPUser(ctx context.Context, user *user.User) error {
+	return bridge.serverManager.AddSMTPAccount(ctx, user.GetSMTPService())
+}
+
+// removeSMTPUser disconnects the given user from the smtp server.
+func (bridge *Bridge) removeSMTPUser(ctx context.Context, user *user.User) error {
+	return bridge.serverManager.RemoveSMTPAccount(ctx, user.GetSMTPService())
+}
diff --git a/internal/bridge/smtp_backend.go b/internal/services/smtp/smtp_backend.go
similarity index 87%
rename from internal/bridge/smtp_backend.go
rename to internal/services/smtp/smtp_backend.go
index 222b381e..1db137f7 100644
--- a/internal/bridge/smtp_backend.go
+++ b/internal/services/smtp/smtp_backend.go
@@ -15,7 +15,7 @@
 // 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 bridge
+package smtp
 
 import (
 	"context"
@@ -25,19 +25,25 @@ import (
 	"strings"
 
 	"github.com/ProtonMail/proton-bridge/v3/internal/identifier"
-	smtpservice "github.com/ProtonMail/proton-bridge/v3/internal/services/smtp"
 	"github.com/ProtonMail/proton-bridge/v3/internal/useragent"
 	"github.com/emersion/go-smtp"
 	"github.com/sirupsen/logrus"
 )
 
-type smtpBackend struct {
-	accounts  *smtpservice.Accounts
+type Backend struct {
+	accounts  *Accounts
 	userAgent identifier.UserAgentUpdater
 }
 
+func NewBackend(accounts *Accounts, userAgent identifier.UserAgentUpdater) *Backend {
+	return &Backend{
+		accounts:  accounts,
+		userAgent: userAgent,
+	}
+}
+
 type smtpSession struct {
-	accounts  *smtpservice.Accounts
+	accounts  *Accounts
 	userAgent identifier.UserAgentUpdater
 
 	userID string
@@ -47,14 +53,14 @@ type smtpSession struct {
 	to   []string
 }
 
-func (be *smtpBackend) NewSession(*smtp.Conn) (smtp.Session, error) {
+func (be *Backend) NewSession(*smtp.Conn) (smtp.Session, error) {
 	return &smtpSession{accounts: be.accounts, userAgent: be.userAgent}, nil
 }
 
 func (s *smtpSession) AuthPlain(username, password string) error {
 	userID, authID, err := s.accounts.CheckAuth(username, []byte(password))
 	if err != nil {
-		if !errors.Is(err, smtpservice.ErrNoSuchUser) {
+		if !errors.Is(err, ErrNoSuchUser) {
 			return fmt.Errorf("unknown error")
 		}
 		logrus.WithFields(logrus.Fields{