If you’re on Windows, certain antivirus, including Defender, can absolutely kill Thunderbird’s performance. There seems to be some kind of lock contention goin

If you’re on Windows, certain antivirus, including Defender, can absolutely kill Thunderbird’s performance. There seems to be some kind of lock contention going on, and the result is Thunderbird taking a long time to do common tasks. Excluding the profile folder from antivirus would solve the issue, with the caveat that any incoming attachments would no longer be automatically scanned.