I have a dedicated server running Centos 6.3. My customer wants to use Microsoft Outlook to send and receive e-mails. He can connect and receive his mails but when he tries to send e-mail he can't because in Turkey SMTP outgoing port 25 is blocked. I need to change the SMTP outgoing port to 587. How can I change it on my server allow mail to be sent?
What you're actually doing is asking how to set the ports used Postfix so that it is also listening on tcp/587, which is the "submission" port.
I have the following in my /etc/postfix/master.cf:
The first column of the first line specifies the service (e.g., the port from /etc/services), listening as an Internet service, using the smtpd command. The various "-o" lines are the options on the smptd command, which specify encryption, SASL authentication, etc. So, my Postfix server will listen on port 587, with SSL and client authentication required.
Your customer will need to adjust his Outlook settings so that the connection is to tcp/587 (Outlook is what we would usually say is outgoing, as the client initiates the connection; the connection for Postfix would be termed incoming), turn on SSL and authenticate against the server.