I use Gmail with Thunderbird, which is working great, except for the part where I get a new email. It shows me the new email twice when notifying because it appears in both the inbox and All Mail folders. I know I can just unsubscribe to the All Mail folder, but then I can't back it up like many people do with Thunderbird. How do I set Thunderbird to notify me of new emails in only certain folders?
Maybe it is possible with filters and the FiltaQuilla Add-on? The add-on adds many new filter actions and one of them is to disable notifications. You could try to add a new filter rule without conditions, action “Do not notify” and then apply it to the All Mail folder. (I haven’t tried it myself.)