HOWTO: Postfix Drops Outbound External Mail
While testing an application, a user requested that I configure the mail server to only deliver to addresses within our company, but drop all mail sent outside. (We don’t want to accidentally bother customers.)
I was a little frustrated by this problem, but now I have a solution. The trick is to set up a transport map that leaves mail destined for our local domain as-is, but then drops everything else.
First, set up a transport file:
# cat transport mydomain.com : .mydomain.com : * discard:
Map it:
# postmap transport
Configure transport_maps in main.cf:
transport_maps = hash:/path/to/transport
Reload Postfix and send test messages. The discard service successfully “delivers” messages straight to the trash, like so:
Sep 15 14:55:10 myhost postfix/discard[16189]: 6F0A22E04E: to=<dannyman@toldme.com>, relay=none, delay=0, status=sent (toldme.com)
