Emails with pictures not sent with not very informative error message

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 version

6.801

Where did you get the app from?

F-Droid

Android version

13

Device model

Realme

Steps to reproduce

Compose Email with some images, even moderate size like 2x130kb. Images usually compressed with imagepipe or similar.

Sender and receiver both Gmail.

After a while I see the notification "Failed to send some messages/unable to send message" and the message is stuck in outbox.

Trying to resend it many times will never fix the problem. Network is better than enough. Sometimes moving to drafts, re-editing and re-sending helps. Most of the time I have to remove the attachments and then it works immediately.

Error message is not informative but best guess the Gmail server considers the email malformed or illegal?

Expected behavior

Send message or provide detailed error message.

Actual behavior

Doesn't send with poor error message.

Logs

Have enabled debug logging but was not asked where to save the logs and don't see export logs option ... willing to retry of course

Start by reproducing the failure on Thunderbird for Android 6.801 with Android 13, Gmail accounts, and image attachments. Enable and export debug logs if possible, then trace the send failure; done means the message sends reliably or the app reports a detailed, actionable error instead of leaving it stuck in the outbox.