What is it you are trying to accomplish by changing the port?
I'm not sure if this solution will suffice but what I did was the following:
1. Setup new service called SMTP_NAT using the appropriate protocol and a non-reserved port.
2. Setup a NAT rule using that newly defined service which accepted the connection and forwarded it to the standard SMTP Proxy.
Again, not sure if that is what you're looking for? Perhaps more information on your part would be helpful.
What is it you are trying to accomplish by changing the port?
I'm not sure if this solution will suffice but what I did was the following:
1. Setup new service called SMTP_NAT using the appropriate protocol and a non-reserved port.
2. Setup a NAT rule using that newly defined service which accepted the connection and forwarded it to the standard SMTP Proxy.
Again, not sure if that is what you're looking for? Perhaps more information on your part would be helpful.