I have a new issue with Thunderbird v.52.3.0 32-bit on a Windows 7 Pro 64-bit PC. I use it for three gmail accounts, but I'm only having the issue on one of the accounts. Some (not all) new messages automatically get moved to the Archive folder. I tell Thunderbird to move the email back to the Inbox and it does, but within a few seconds, it automatically moves it back to the Archive folder, just like it would if a filter were set up to move certain messages to a specific folder. It doesn't appear to be dependent on the sender or type of message though. For instance, I received a UPS notification email yesterday and it was automatically sent to the Archive folder. I received the same UPS notification email today and it wasn't sent to the archive folder. The messages that get moved to Archives in Thunderbird do show up in the Inbox, as it should, on gmail.com, outside of Thunderbird. There are no filters set up on the gmail account or in Thunderbird for this particular email account. I know Thunderbird isn't supposed to be able to automatically move messages to Archives, so I'm stumped as to why it's happening. I have two other gmail accounts set up in Thunderbird and it doesn't happen on the other two accounts, just this one, so I doubt it's being caused by a compatibility issue. I see there is at least one other user who posted with the same issue recently but no resolution was posted. Thank your for any assistance.