Change smtp server port?

[MarcoV]

I installed my server with the debian 3.1 perfect setup and configured it to all my needs.
But my internet provider blocks outgoing smtp traffic (port: 25) can i change this to another port so i can use the smtp server? and i also like to what files that i need to change.

[falko]

Originally Posted by MarcoV

can i change this to another port so i can use the smtp server? and i also like to what files that i need to change.

Theoretically yes, practically no. If you change the port you won't be able to connect to other email servers because they listen on port 25...

You could set up a second server in a data center that listens on a different port (e.g. 443) to pick up your emails and then sends them out on port 25 - but if you have a "real" server in a data center than you don't need the server in your home LAN anymore, i guess...

[StefanV]

But what about a NAT from port 26 to port 25? I did something like this and I didn't had any problems until now... but today I've just launched the server into production.. should I expect to have problems?

[till]

The external port for smtp must be port 25, otherwise you will get the problem that your server will not get any external emails.

[StefanV]

Yeap but the limitation is only on MarcoV side.. from his ISP. So, he can let SMTP on port 25 for everybody else to connect to that port and for him to be able to connect, he makes a port forwarding (not NAT like I've said in the previous post) from port 26 to port 25. And he sets his mail client to connect on port 26.