GODT-2266: Pause event stream while sending

internal/user/smtp.go

@@ -158,7 +158,7 @@ func (user *User) sendMail(authID string, from string, to []string, r io.Reader)
 
 			return nil
 		})
-	}, user.apiUserLock, user.apiAddrsLock)
+	}, user.apiUserLock, user.apiAddrsLock, user.eventLock)
 }
 
 // sendWithKey sends the message with the given address key.

internal/user/user.go

@@ -60,9 +60,11 @@ type User struct {
 	vault    *vault.User
 	client   *proton.Client
 	reporter reporter.Reporter
-	eventCh  *queue.QueuedChannel[events.Event]
 	sendHash *sendRecorder
 
+	eventCh   *queue.QueuedChannel[events.Event]
+	eventLock safe.RWMutex
+
 	apiUser     proton.User
 	apiUserLock safe.RWMutex
 
@@ -120,9 +122,11 @@ func New(
 		vault:    encVault,
 		client:   client,
 		reporter: reporter,
-		eventCh:  queue.NewQueuedChannel[events.Event](0, 0),
 		sendHash: newSendRecorder(sendEntryExpiry),
 
+		eventCh:   queue.NewQueuedChannel[events.Event](0, 0),
+		eventLock: safe.NewRWMutex(),
+
 		apiUser:     apiUser,
 		apiUserLock: safe.NewRWMutex(),
 
@@ -548,6 +552,9 @@ func (user *User) initUpdateCh(mode vault.AddressMode) {
 
 // doEventPoll is called whenever API events should be polled.
 func (user *User) doEventPoll(ctx context.Context) error {
+	user.eventLock.Lock()
+	defer user.eventLock.Unlock()
+
 	event, err := user.client.GetEvent(ctx, user.vault.EventID())
 	if err != nil {
 		return fmt.Errorf("failed to get event: %w", err)