I'm trying to set PAT for an SMTP server which I'm told only can only run on the standard port 25 on the server, however as this is blocked by many ISPs, I've been asked to set up a translation on the firewall (PIX 525 running software v 8.04) for traffic coming in towards the server on port 225 to 25 which is fine and I'm able to do this however it also needs to accept connections on 25 still also which is where I'm running into problems.
A static translation such as the following stops port 25 being reachable directly because the pix is translating the source port to 225 for return traffic, so although it is reachable on port 225 its not reachable on 25 because of this command.
static (inside,outside) tcp 217.*.1.43 225 217.*.1.43 smtp netmask 255.255.255.255
Any advise on how to PAT but also not PAT would be appreciated.