spam started to get out of control on our servers, and as good of a job as spam assassin does it was just starting to become too much for us to manage on top of all of our other day to day operations, so we switched to using postini for our anti-spam filtering.
now in order to get it fully working properly i have to block off all access to my server on port 25 except from Postini's netblocks. Since I have clients also using this port to authenticate SMTP for relaying I need to set them up on a different port to use, like 2500. However, I want to setup this other SMTP auth port to only do SMTP auth and not allow any spammers to figure out they can relay their spam and bypass Postini on that port.
I'm running NE so is there any supported way to do this?