I have an IMAP email account currently running on Thunderbird, which was previously a POP account that I switched over (same server etc., only changed how Thunderbird handled the account). Since I made the switch, any message filters I run that move messages into a specific IMAP folder will execute, only for the messages to promptly pop back out of the folder and into the inbox again. As an example, I have a message filter set to automatically move emails coming from an IFTTT reddit alert into the "social" IMAP folder. When the filter runs, the emails in question disappear from the inbox and the new mail counter for the "social" folder goes up accordingly. But after 2-3 seconds, the "social" counter goes back down, the emails reappear in the inbox, and the status bar at the bottom says "Moved X messages from social to Inbox". Running the filter on individual messages instead of the whole inbox makes no difference. I've triple-checked my filters to make sure that there aren't any conflicting filters that might be moving the emails back to the inbox (there aren't). The weird thing is that if I select the emails in question and _manually_ move them from the inbox to the "social" folder, the move sticks and they don't pop back. Filters that don't move messages and instead perform actions like applying tags or deleting emails work as intended. Installation and setting details: * Thunderbird v52.9.1 64-bit * OS Ubuntu 18.04.1 LTS 64-bit * Profile & settings synced via Dropbox v56.4.94, *minus* the Mail and ImapMail folders. I was trying to get rid of the thousands of popstate files generated by syncing a Thunderbird POP account via Dropbox. (Eliminating Dropbox entirely isn't an option; I have a bunch of important message tags etc. that I also need preserved, so they have to be synced between my devices.) * (checked) Check for new messages at startup * (checked) Check for new messages every 10 minutes * (checked) Allow immediate server notifications when new messages arrive * When I delete a message: Remove it immediately * (unchecked) Keep message archives in * (unchecked) Keep messages for this account on this computer * (checked) Synchronize all messages locally regardless of age * (checked) Don't delete any messages * (checked) Always keep starred messages I suspect the issue might have something to do with my jury rigged Dropbox setup, but as previously stated, I need some sort of method to sync tags and preferences between devices. Any suggestions for alternative setups that would allow for that would be welcome.