How to Stop Postfix from Listening on 'localhost'

(UP)

Even with the "Mail" service disabled on OS X 10.4, Postfix still tends to listen on the "localhost" port 25. Sometimes, Kerio admins want to disable this.

The problem is a checkbox which is grayed out under the Mail settings in ServerAdmin.
The checkbox is, ServerAdmin-->Mail-->Settings-->General-->Enable SMTP-->Allow incoming mail

To disable Postfix from answering on localhost:

  1. Check the "Enable SMTP" checkbox.
  2. Uncheck the "Allow incoming mail" checkbox.
  3. Uncheck the "Enable SMTP" checkbox.
  4. Reboot