Deleting email does not synch with Windows Thunderbird

I use current Thunderbird (TBird) on my Win11 desktop PC. I just installed the current K9 Email on my Android 14 phone. My Email is IMAP, and I have set up K9 for Push notifications.

A major problem with K9 is that deleting emails from my Inbox is not synchronized/reflected on my TBird Inbox. In particular, I deleted 3 emails on K9 and when I opened TBird several hours later those 3 emails were still there. So this leads to 2 questions:

  1. When K9 deletes an email, where does it actually go?

  2. Is there a way to make K9 deletions immediately synch with my IMAP server so my phone and desktop stay i synch.

Let me know if there is any additional info I can provide to help resolve this issue.

My guess would be that your IMAP server didn’t tell K-9 which folder is the trash folder. You can change it on settings → account → folders → trash.

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Nope - that didn’t fix it. I made the update you suggested but got the same results: deleting (using right sweep) deleted the email from the K9 inbox (I still have no idea where it went), but was still in my TBird folder as well as in Bluemail’s Inbox on my phone.

When I deleted it in Bluemail it got deleted from the IMAP Inbox and showed up in the IMAP Trash folder.


Well darn! I thought I had it fixed when I found out how to make all my folders Class1. But that did not fix it - After making them all Class 1 the behavior was just as before.

Maybe K9 isn’t really ready for prime time yet. That’s why I’ve kept Bluemail on my phone.

While I can’t speak to your issue, K-9 has been fit for use as a daily driver for over a decade. I’ve used it continuously on every Android device I have owned since 2011.

I wish I had some suggestions for you to try, but I have never had any unexpected behavior with deleting messages.


Well, I went back and re - did all the classes for my folders and this time it worked. Looks like I missed something the first time I did this.

I guess it would be helpful for other new users to be told this is something that needs to be look at when setting up a new account.