By default MDaemon will listen for incoming SMTP connections on port 25.
If this port is being used by another application or firewall restrictions prevent this port being used locally then you can change the port MDaemon listens for incoming SMTP connections on by changing the value in Setup -> Server Settings -> DNS + IPs -> Ports:
Once you have changed the port number it is important that you click “Bind to new port values now” to ensure the changes are applied.
