ipfw and mail

[Gustavo A. Baratto]

Hello guys,

some of our users' ISPs don't allow them to use port 25, so they cannot use out mail server.

I want to open a new port (2525) and forward all packets from 2525 to 25 so, they can use mail.

I tried this in IPFW:
0100 119649 44772439 allow tcp from any to me dst-port 25 keep-state
0200      0        0 divert 25 ip from any to me dst-port 2525 keep-state
0300 103075 35531648 allow ip from me to any keep-state
0400     60     4530 deny log ip from any to any


If I telnet directly to port 25, I can get the prompt, but if I telnet to port 2525, I get a connection refused.

What should I do in ipfw to forward port 2525 to port 25 tranparently?

Thanks