I've an interesting problem that I thought was straightforward, but turns out I think I'm whistling down the wrong path.
It has to do with (shudder) email. I thought I was done with needing to know about email guts ten years ago; I was wrong.
Simply put, I need to figure out how to relay outgoing email that is not targetted in our domain from our domain into a 'dropbox' in a DMZ, and the Other Guys can retrieve that email from their side of the DMZ and distribute it accordingly, even out to the public internet if need be. There will be no [un-established] traffic coming back to Our side from anywhere; any attempts to do so are dropped with malicious prejudice.
Our side is postfix running on scilinux6.1. The DMZ boxes are redhat5.4. The Other Guys are M$ Exchange. The firewalls are set up such that data can go from Our Side downsec to the DMZ, but not upsec from the DMZ into Our Side. Same for the Other Guys.
My first thinking was simply to set up postfix on a box in the DMZ and tell them to set up fetchmail or whatever the M$ equivalent is, but then I started remembering that postfix wants to actively relay email onwards, rather than hold it and wait for someone to 'reach in' and retrieve it.
I'm not sure I've explained this well, but hopefully it's clear enough that someone can point me in the right direction. I seem to remember having done this before, but it was a looong time ago.