Follow the steps below if you want to change the outgoing mail port for Plesk:
1. Create a copy of smtp_psa by entering:
1. # cp /etc/xinetd.d/smtp_psa /etc/xinetd.d/smtp_nonstandard
2. Add these lines to the copy you just made:
1. type = UNLISTED
port = 2525 < Port to which smtp service should bind >
and change the service name to match the name of the file.
3. Restart xinetd:
# /etc/init.d/xinetd restart
You should now be able to send mails through port 2525. You can choose any other port, if needed.