How to change PowerMTA SMTP port

smtp-port specifies the TCP port number to use for listening for incoming SMTP connections, allowing you to run PowerMTA on a non-standard port. 

Default:
25 (standard SMTP port)

This can be useful if a second mailer handles all incoming traffic while PowerMTA is fed through another TCP port.

If smtp-port is set to 0, PowerMTA does not listen for incoming connections (and feeding is only possible through the submission APIs).

Example:
# use port 2525 since port
smtp-port 2525

Another way: