thunderbird is vulnerable to downgrade attack. Remote attacker is able to take control of the authenticated session and execute SMTP commands resulting in a man in the middle attack.
access.redhat.com/errata/RHSA-2021:3839
access.redhat.com/security/updates/classification/#important
bugzilla.mozilla.org/show_bug.cgi?id=1733366
bugzilla.redhat.com/show_bug.cgi?id=2013469
lists.debian.org/debian-lts-announce/2022/01/msg00001.html
www.debian.org/security/2022/dsa-5034
www.mozilla.org/security/advisories/mfsa2021-47/