mail router/proxy/hub/exhanger/switch ???!!!

[quantumMoose]

Hi, we are running a few mailservers behind one router. I am currently using a piece of software called Moxy Mail Proxy to route incomming mail on port 25 to whichever mailserver, depending on the domain its destined for, eg mail for org1.com, org2.net and org2.org all goes to the same initial proxy then gets redirected to their respective email servers. However, this piece of software is far from perfect, as it goes mad after a short while (few hours) opening many, many (too many) file handles/network sockets and brings the systm to a halt. I have been trying to debug this, while at the same time try to find another (more popularly used, and supported) program to do the trick, but i dont know what i am really looking for (is this a mail proxy, mail router or what). If anyone gets the general gist of what i am looking for, and what i am trying to do, and knows of such a piece of software or at least what to look for, please get in touch.

Thanks
-quantumMoose