Recently (over 2 weeks now) many people (myself included: https://forum.avast.com/index.php?topic=218267.0) had the issue that Avast! deleted Mails stored in Thunderbird.
It mostly detects Phishing, even if false positive, and then deletes the whole file that contains the mail.
There are several bugs here, the most critical might be that Avast! deletes the file completely without asking and with no option to restore it. (Move to Chest fails with “Error 112 in s_NewFile”
and “Error 112 in chestAddFileRpc”).
Reporting any bug to Avast! is futile, you are simply ignored. I tried mailing 2 staff contacts, submitting in false positive, and contacting a guy that works for Avast in forums. I got absolute ZERO response.
The community isnt much help either, mostly blaming the user for not shifting data away from the deleted file and suggesting what you could do in the future, ignoring the bugs in Avast. I mean they cant help because they have no contact to the devs, as the company outsources the support to the community.
This ignorance led to me uninstalling Avast! after over 10 years. The company doesnt care if its product is flawed and they dont care if you loose data. So I dont see any value in keeping it on my system.