Listen Port and Network Interface card
How to change the listen port and force Postfix to listen specific network addresses ?
- On the Postfix MTA system, select "Routing & network" tab.
- Click on the Postfix Network settings.
- By default the Postfix main systems listen all interface.
- To specify one only, click on Add button.
- Choose the local IP address in the drop-down list or specify your interface.
Not the port filed is not attached to the interface, if change the port, it will be changed for all interfaces set.
This parameter is the network interface addresses that this mail system receives mail on.
When interfaces specifies just one IPv4 and/or IPv6 address that is not a loopback address, the Postfix SMTP client will use this address as the IP source address for outbound mail.
Support for IPv6 is available.
On a multi-homed firewall with separate Postfix instances listening on the "inside" and "outside" interfaces, this can prevent each instance from being able to reach servers on the "other side" of the firewall.