Using CLI "mail" command

What I just learned...

Thunderbird 91.*.* (Ubuntu 21.10) has removed movemail support, so all access to my localhost mbox's is gone. See Ubuntu 21.10 - Thunderbird 91.x.x drops (movemail) mbox support! for some background info.

When using CLI mail, after reading message(s), read messages are moved from /var/mail/al to /home/al/mbox.

If I use mail -f /home/al/mbox I can now read old, previously read, mail messages.

If I symlink /home/al/mbox to /home/al/.thunderbird/kzn2n9g5.default/Mail/Local\ Folders then I can read them using Thunderbird. Read the previous link for more details about this.

ln -s /home/al/mbox /home/al/.thunderbird/kzn2n9g5.default/Mail/Local\ Folders/mbox-home

Update #1:

If I create /home/al/.hidden with the contents mbox then I won't have to look at the mbox file in Nautilus.