Occasionally getting "error - Unable to send message" on reply

Checklist

• I have used the search function to see if someone else has already submitted the same bug report.
• I will describe the problem with as much detail as possible.

App

K-9 Mail

App version

9.0

Where did you get the app from?

F-Droid

Android version

OxygenOS 15 (Android 15)

Device model

OnePlus 12

Steps to reproduce

1. Reply to an e-mail using K-9.

Expected behavior

1. Reply to an e-mail using K-9.
2. Message gets to Outbox.
3. Mail gets delivered successfully
4. Message gets transferred to Sent

Actual behavior

1. Reply to an e-mail using K-9.
2. Message gets to Outbox.
3. Mail gets delivered successfully (checked the SMTP logs on the server)
4. Message stays in Outbox and doesn't go to Sent, resulting in an error notification (reappearing constantly until I delete it from Outbox).

Logs

k9mail-logs.txt

05-28 10:50:42.910 29067 29252 I MessagingController: Running command 'sendPendingMessages', seq = 475 (background priority)
05-28 10:50:42.910 29067 29252 E AbstractWindowedCursor_getLongdebug: Error_Msg read row:0columnIndex:3
05-28 10:50:42.911 29067 29252 I MessagingController: Scanning Outbox folder for messages to send
05-28 10:50:42.912 29067 29252 V MessagingController: Skipping sending message K9LOCAL:94a9335d-b83f-41d4-8fc5-5eb3b357296b (reason: error - Unable to send message)
05-28 10:50:42.916 29067 29067 D AppWidgetProvider:  ACTION_APPWIDGET_UPDATE, appWidgetIds: [7]
05-28 10:50:42.917 29067 30221 I AppWidgetManager: updateAppWidgetIds, mPackageName: com.fsck.k9, appWidgetIds: [7], views:android.widget.RemoteViews@da4404c
05-28 10:50:42.920 29067 29252 I MessagingController:  Command 'sendPendingMessages' completed

Start with the attached logs and the MessagingController sendPendingMessages entry point, focusing on the Outbox scan and the logged “Unable to send message” skip. Reproduce the reply flow and trace why a message already delivered by SMTP remains in Outbox; done means it moves to Sent without repeated error notifications.