SquirrelMail has been puking out errors when mail with MIME attachments is read since we updated our web server to Ubuntu 18.04 LTS and PHP 7.2.

     The update to PHP7.2 required an upgrade of squirrelmail, the upgrade of squirrelmail brought those messages.  I was able to chase this down to a DEBUG flag the developers left enabled and turn it off.

     If you are being overwhelmed with spam there are some things you can do to adjust spam filter sensitivities or whitelist or blacklist particular addresses:

https://www.eskimo.com/support/mail/spam-control-facilities/