Post fix restart produces the following

# tail -f /usr/local/psa/var/log/maillog
Mar  4 21:40:07 postfix/postfix-script[24660]: fatal: the Postfix mail system is not running
Mar  4 21:40:08 postfix/postfix-script[24731]: starting the Postfix mail system
Mar  4 21:40:08 postfix/master[24732]: fatal: bind 0.0.0.0 port 25: Address already in use

Look for multiple instances of smtp inet n – n – – smtpd and comment them out:

#smtp inet n - n - - smtpd
localhost:smtp inet n - n - - smtpd
smtp_bind_address6= -o smtp_address_preference=ipv4
#smtp inet n - n - - smtpd

Restart postfix

# service postfix restart