[Cialug] Postfix docker fix

[L. V. Lammert]

Trying to get the maxking django docker to send proper emails, .. the
"SERVE_FROM_DOMAIN" is ignmored in the local settings, .. and when placed
in the compose environment it crashes the container.

The only way I can figure out to fix it is by having Postfix replace a bad
URL with the correct one on any outbound email. Is there a way to create a
simple milter out of a sed command?

	Thanks!