Hi all i need a bit of help with a problem i'm having basicly what i need to do is find a way to make postfix recieve mail on a different port so i can get passed a problem with an ISP stopping all port 25 traffic unless to there mail server any ideas?.

I don't think you will be able to do this because any server that tries to deliver mail will only try port 25. If you only want to use it for the client side where you can configure the client software then it should be possible.

As they said before, all other mail servers will send email through port 25. But if you still want to change it here's how:

Add a line to your /etc/services:

smtp2 5000/tcp

Now edit your /etc/postfix/master.cf so the smtpd line starts with smtp2:

smtp2 inet n - n - - smtpd

Restart Postfix.

I will say that this worked for me on a Linux Red Hat 9 box, but it would only respond locally, that is, it would not accept connections through that port from any other machine on my network. I am still trying to figure out why.

tcpwrapper, maybe? Perhaps you have to edit /etc/hosts.allow for the new port.

Well, after much head-banging and cursing I finally discovered the problem:

Being new to postfix I didn't know about this entry in main.cf:

inet_interfaces = localhost

It means that postfix will only listen to the localhost for any connections! No, why postfix comes like this out of the box is (idiotic) and beyond me. But like I said, I'm new to postfix. Changing that to inet_interfaces = all and restarting postfix did the trick.