HOW TO CONFIGURE POSTFIX TO LISTEN PORT 25 AND PORT 26 TCP PORT


We will start modifying postfix conf so postfix will listen to port 25 and port 26 TCP.
First, login into the server with root access
I assume your postfix configuration is stored in /etc/postfix
So we just need to edit master.cf

#vi /etc/postfix/master.cf

### add this line below under ###

smtp      inet  n       —       n       —       —       smtpd
26          inet  n       —      n       —       —   smtpd

save this files and we just need to reload the postfix mailserver

#postfix reload