Permission denied

[Ken Wright]

My server has been running just fine for over a year, until I upgraded
PostfixAdmin and somehow messed things up.  Now I can't log in, and my
mail client (Evolution, if it matters) keeps popping up an
authentication request.  The server is Ubuntu 20.04, my Dovecot is
version 2.3.7.2, and Evolution is 3.40.4-1.  I've also tried logging in
with Roundcube with no success.  Any insight or suggestions will be
gratefully received!

Here's the most recent entry from /var/log/mail.err:

Dec 28 22:05:02 grace dovecot:
lmtp(me at mydomain.com)<910309><SOFiMl7Qy2Hl4w0AThsuZQ>: Error: lmtp-
server: conn unix:pid=906625,uid=117 [6]: rcpt me at mydomain.com: Mailbox
INBOX:
open(/var/mail/vmail/me at mydomain.com/tmp/1640747102.M850878P910309.grac
) failed: Permission denied

Any further information available upon request!