All is well after a reboot. Thanks, Till.
Amavis is quite a memory-hog. This is the third time in as many weeks that Amavis has chewed-up all available RAM (over 500MB, on average) and caused this server to tank.
As there seems to be no means by which to limit Amavis's memory consumption directly, might you have a recommendation for achieving the desired result by alternative means?
Not to digress, but Amavis's memory usage skyrocketed one time because an end-user had sent a group email in which the recipients' email addresses contained angle-brackets, e.g.:
Apr 5 09:29:33 localhost postfix/smtpd: warning: Illegal address syntax from unknown[XXX.XXX.XXX.XXX] in RCPT command: <'email@example.com'>
The message was re-queued repeatedly, eating-up more RAM each time, until memory was exhausted and the server crashed.
I would really like to prevent Amavis from being a constant risk to the rest of the server.