Thunderbird 78
Advisory of fix for my setup that may help someone else:
Fedora 33 with XFCE4 spin. Installed this fresh last week which updates the OS repo version of Thunderbird to 78. I have since then noticed that all contacts who have successfully sent me attachments in the past (mainly their PDF remittance notifications) are not showing the e-mails as having any attachments. Examining the source of the e-mails shows this is not a 'winmail.dat' thing and the only thing that changed for me is updating Thunderbird with the newer Fedora installation.
Solution: Ran an 'rpm -ev thunderbird' and downloaded version 68.6.0 (Fedora 32 x86_64 package) and "rpm -iv" installed it. Back to normal with attachments once again accessible. Package that works fine is:
thunderbird-68.6.0-1.fc32.x86_64.rpm
From:
https://rpmfind.net/linux/rpm2html/search.php?query=thunderbird