How do I enable port 587 (submission) in Postfix?
To enable port 587, edit the file /etc/postfix/master.cf and remove the # in front of the following line:
#submission inet n – n – – smtpd
so that it looks like this:
submission inet n – n – – smtpd
and restart postfix
Also be sure to open port 587 on your firewall.