I agree that breaking an existing profile when upgrading with no way of recovering it after downgrading is very user-unfriendly. That said it's an upstream decision, and it was documented in the upstream release notes: https://www.thunderbird.net/en-US/thunderbird/91.0/releasenotes/.
-- You received this bug notification because you are a member of Desktop Packages, which is subscribed to thunderbird in Ubuntu. https://bugs.launchpad.net/bugs/1946606 Title: thunderbird 91 does not support movemail Status in thunderbird package in Ubuntu: Won't Fix Bug description: Thunderbird 91 does not support local Unix Mailspool (Movemail) accounts. This is apparently a well-known upstream decision, but is not documented in the Ubuntu changelog for the package, and the sudden absence of a local mail account is rather jarring to experience. > remove movemail support https://bugzilla.mozilla.org/show_bug.cgi?id=1625741 https://hg.mozilla.org/comm- central/rev/931a1fb770eb9bf6d2b99c7afcf07521376a5da4 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/thunderbird/+bug/1946606/+subscriptions -- Mailing list: https://launchpad.net/~desktop-packages Post to : [email protected] Unsubscribe : https://launchpad.net/~desktop-packages More help : https://help.launchpad.net/ListHelp

