Originally Posted by BoloMarkIII
I got my server the sniff both ports 25 and 587 no problem, the problem is that the ISP also uses port 587
uses only or really blocks? there is simply no reason to block it, even they have enabled it on their server too. if they really have blocked it, most likely they block 465 too.
try to find out free port and use fuinha's hint and redirect that port to postfix. you can make those kind of redirects as many as needed, so in the end your server will listen pretty many ports and all your clients will be happy.
common extra ports are 8025 and 8825.