I'm using Thunderbird 115.10.1 and Windows 11 Pro. Thunderbird has suddenly started sending my partner's emails to Trash. We've been emailing fine for years before this. She has not changed anything in her emailing. I've closed and re-opened Thunderbird. Her emails are not marked as Spam and I have marked some of them as 'not junk'. Anyone got any ideas? I can't seem to find reference to other people having this problem.

PS It's only her emails this is happening to. All other valid ones are OK.

PPS her emails are from a Gmail account but emails from other people with Gmail accounts don't go to Trash.

Did you happen to have any message filters setup that copied or moved her emails to a particular folder? If so, might make sure it's not sending it to trash now all of a sudden.

Unless there's some message filter acting on them, I would expect them to stay in the Inbox.

That's a fair point Mark, but no, in this case there are no filters testing for any part of her email address.

Thunderbird by default "whitelists" email addresses in your personal address book. You can also set any or all address books to act as a white list in account settings for the account.

In recent years we have seen a large uptick in folks that are not aware their email provider usually has their own spam filtering and that they frequently move mail to a spam folder without any input from Thunderbird. I have even heard of yahoo mail moving mail back to the spam folder once you say it is not spam and move it somewhere else. Yahoo also do not offer any "Opt out" for they spam filtering. I feel that this is your issue, as the emails marked as spam server side regularly are not marked as spam in Thunderbird spam folders, let alone the trash if they get that far. But I would not exclude the antivirus issues just yet as direct movement to the trash bypassing the spam folder often is an indicator of failure there.

In the past there have been significant issues caused by antivirus spam and scam filters messing up big time in Thunderbird as they are written towork with one version of Thunderbird only and it updates monthly. The result being mail marked as spam and going directly to trash or just going directly to trash. Best advice there is just disable any antivirus scam or spam filtering in the antivirus application.