28.4 Firewall/Router Configuration

Since the sending and receiving of email messages involves network connections, the firewall-cmd tool will need to be used to add the smtp service to the firewall as follows:

# firewall-cmd --permanent --add-service=smtp

It will also be important to configure any other firewall or router between the server and the internet to allow connections on port 25, 143 and 587 and, if necessary, to configure port forwarding for those ports to the corresponding ports on the email server.

With these initial steps completed, we can now move on to installing Postfix.