I am using Thunderbird 91.3.2. On my IMAP account, Thunderbird is deleting all messages older than one month, even though for the account I have checked the box "Don't delete any messages" under "Syncroniztion and Storage." Each day I go in, I see that all messages older than 30 days are deleted. I'm confident Thunderbird is doing it: I checked the Activity Log this morning, and it says that 27 messages were deleted, which would be all the messages from 31 or more days ago. Is there another setting that overrides the one in Syncronization and Settings? or that would be responsible? In short, how can I get to the bottom of this? I need to retain older messages, which has invoices and other information.