Minimal MX Mail and Proxy Confusion

[Steve Craft]

Slightly OT -

My proxy server has 3 "holes" through it passing port 23,25,143 traffic
directly to my qmail box.  I am trying to get the mail traffic to my mail
server from both sides of the proxy.  Can anyone example me the minimal DNS
MX record entry/entries necessary to make this work?  Thanks if you can
help.