I have found a partial solution - a workaround. It's not perfect, but it works.
On my machine, local email is delivered to ~/.localmail. /var/spool/mail/<myname> is a link to ~/.localmail.
In Thunderbird 78, I had an account that fetched data from ~/.localmail. This doesn't work anymore in Thunderbird 91, since Thunderbird dropped support for movemail.
I followed the suggestion given in comment #35 of this thread:
https://bugzilla.mozilla.org/show_bug.cgi?id=1625741. I added a Link to the data directory of my regular Thunderbird account to ~/.localmail:
Code: Select all
cd ~/.thunderbird/8eda639c.default/Mail/<myaccount>
ln -s ~/.localdir LocalMail
Result: in Thunderbird, there's a new folder "LocalMail" which allows me to read and manage incoming local emails. I cannot send local emails - but that's no problem, because I'm mostly interested in receiving system emails from cron, smartmontools, etc.