Mail relay through Windows Server 2003

Question

I work in a communications department at a small university.  I'm running a Mac network sandboxed inside of the main institution's Windows network.  All of my macs are connected to an XServe and all services except internet access are controlled via my XServe.  We're connected to the internet through a router between my network and the main institution's.  We're set up this way because the IT department won't touch macs, so they pushed all the mac stuff onto me (I don't have a computer science degree or anything of that nature, just an interest and a couple server certification classes).
Anyway, I have a small web-based app that handles gear checkout.  For simplicity, it only works on my intranet.  However, it's designed to send emails to appropriate people for different things (when gear is checked out, if there's a problem, etc).  The problem is that these emails must be relayed through IT's server.  They're telling me that they can't set their server up to relay email from mine without making it an open relay (which, obviously, none of us wants).
My question is, is it really that difficult to allow email to relay from a specific address on Windows Server 2003?  On my mail server, I readily found a "Allow relays from these address only" section and seems this is exactly what would be needed on their side--I can't imagine it's much more difficult or generalized than that on their end.
Here is the log entry on my server when an email is attempted to send.  Is there something else I should be looking at besides the relay?
Mar  8 10:03:28 MYSERVER postfix/smtp[12631]: 3C02EE81654: to=<[email protected]>, relay=IT.MAIL.SERVER[192.168.x.x]:25, delay=0.01, delays=0/0/0.01/0, dsn=4.7.0, status=deferred (SASL authentication failed; cannot authenticate to server IT.MAIL.SERVER[192.168.x.x: generic failure)

Answer 1

They're telling me that they can't set their server up to relay email from mine without making it an open relay
Then they're even stupider than your opening paragraph implies. Seriously. If they cannot setup their mail server to accept and relay mail from a specific IP address they really should be looking for other jobs... no, other careers entirely, since they have no idea what they're doing. Or, at least, no interest in what they do.
Indeed, a google search finds a Microsoft Technet article as the first hit. I believe item #4 on that list is exactly what you need. And I don't even do Windows!