By default SMTP usually uses port 25, but as sometimes ISP’s may prevent the port 25 for access. In such circumstances we need to set up an alternate port of SMTP. This can be done on a cPanel servers as follows:
Login to the WHM.
Navigate to Main >> Service Configuration .
Click on service manager.
Navigate to the section which says “exim on another port”.
Click on the “Enabled” box besides the setting and enter the Alternative SMTP Port in the box and apply changes.
Now make sure the alternative port is enabled on the server firewall.
For this open the file /etc/csf/csf.conf on the server and add the port in the TCP_IN, TCP_OUT, UDP_IN, UDP_OUT sections. Save the firewall and restart the firewall.
Now the alternative SMTP port is configured for your server.
[wpfmb type=’info’ theme=2]If you want to add an alternate port on plesk you can check our article on how to add alternate smtp port in Plesk [/wpfmb]