Obtaining my MX Record

I have successfully be able to now host my own website from my home with a dynamic IP address (thanks to direct update and zoneedit). I am running Windows Server 2003 (was cheaper than Win2k plus the cost of Exchange Server) and use Comcast as my ISP. I can send out mail using my @mydomain.com but cannot receive it. Where would I obtain an MX Record from and how do I use it (if this is even the problem). Also I have opened up ports on my router to accept to my server 192.168.0.XXX (where the POP3 server is running).

Right now I have my MX Record in Zoneedit (zoneedit.com) set up server.envisionnetworking.net handles mail for envisionnetworking.net (Ranked to receive 1st).