I had to configure Sendmail in order for Ubersmith to be able to receive support requests via email. Basically, you configure an alias (/etc/aliases) like so:
support: "|php -q -f /home/html/cron/gateway.php domain.com 1"
This all seemed to be very straightforward. I didn’t even think to test it until hours later. When I finally did test out the support request by email function, I received this very abrupt rebuke from Sendmail in the form of a bounceback: