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How To Change Your SMTP Listening Port

This procedure is an answer to a common problem when an ISP blocks access to port 25 to IP address outside the ISP’s IP range. Often used to combat spam, it creates problems for users who have a need to use an SMTP server other then the one provided by the ISP.

This can only be performed by users with a VPS.

1. First, SSH to your VPS and logon.
2. edit /etc/services, and added the lines
   

   smtp2 26/tcp mail
   smtp2 26/udp mail
   

   
   I also recommend commenting the edited lines for anyone in the future that may need to reverse or
   change the SMTP ports again.
3. copy /etc/xinetd.d/smtp_lxa to /etc/xinetd.d/smtp2_lxa
   

   cp /etc/xinetd.d/smtp_lxa /etc/xinetd.d/smtp2_lxa
   

4. edit /etc/xinetd.d/smtp2_lxa and change the line
   “service smtp” to “service smtp2”
5. Restart xinetd by using the following command:
   

   service xinetd restart
   

Verify that qmail is now listening on port 26 by either configuring your email client to send mail on port 26, or open a telnet session to your mail server, port 26, you should receive an ESMTP hello.