Thank you for your reply ,because some region's ISP reject to visit the port 25 for preventing the user from spammer, so I must change it to another port to let the user in this region can use my SMTP . but how to do it ,pls let me know. Thanks!
so, it are users who want to connect to an unstandard SMTP port number. Right?
Hmm... that can become tricky because ISA server don't support port redirection. That means that the internal SMTP server must run on the same TCP port number as the one you want to publish on.
Assuming you have also to publish the standard SMTP service for accepting inbound mail from the Internet, that would mean you have to run two internal SMTP servers: one for the regular inbound mail from the Internet and one on an unstandard TCP port number for the users.
For the unstandard SMTP service, you'll have to create a custom protocol definition TCP port X inbound where X is the port number you want to use. You have then to use that protocol definition as mapped server protocol in a server publishing rule.