Retention policy not followed

[RandomSF]

I have an IMAP account running in Fossamail. On my Sent and Trash folders I have set a retention policy of 91 days. This is working well on the Sent folder, but the Trash folder is deleting at some other rate. I say some rate because I haven't yet found a pattern. It's about 250 emails and something less than 30 days, but it seems to vary.

I'm a longtime Thunderbird user with several accounts that never showed this. I've used Fossamail for over half a year and it was working well until v25.1.7.

Is there a reason the Trash folder would behave differently from the Sent folder and differently from the past?

[Tharn]

The mail provider may have its own trash retention policy. Usually much less, around a week or two. And if it never happened before, it's still possible that it was recently changed to save space. I'd have a look at the provider settings first, if it's properly set-up in Fossamail.

[RandomSF]

Sorry, I should have mentioned that. I have control of the server and there is nothing server-side causing that. My wife is using Tbird off the same server and her Tbird Retention Policy is honored.

[Tharn]

Okay, that's different. So you have custom retention policies in place for these two folders. That should work.

Look at Account Settings. Synchronization & Storage could have a setting that only syncs recent messages and prohibits older ones from being synced. The Disc Space submenu for Local Folders can also mess with folder retention policies. Junk Settings has a tickable box that deletes messages after X days. But I'm not an expert on these, I just use global settings 'cause I only have one account set up currently.

[RandomSF]

Synchronization & Storage is set to synchronize all.
Local Folders disk space is don't delete any.