As an IT guy with 15 year experience in large corporates, I can say there are many way to provide macs with Exchange email. My background is all Windows and Exchange admin, and I just recently got a Mac to play around with.

Entourage works fine for me, but Outlook 2007 is nicer. I have a work computer (XP with Office 2007), home PC (Vista and 2007), and Mac (Leopard and Entourage 2008), plus a Windows mobile smart phone. All sync with Exchange with no problems, but I agree I find myself clicking send/receive in Entourage due to slow syncs.

There's Outlook Web Access, which is pretty decent when it's MS Exchange 2007 running via Safari. Being web-based, this also equals no Mac knowledge required for corporate IT, which they would probably appreciate.

There's various remote desktop solutions (Microsoft Terminal Server--RDP--and Citrix). They do require your company have a terminal server, but work fine if you need actual Outlook.

Sounds like the poster's IT department is conflicted regarding Macs. All experienced IT people desire to make all users run the same thing in the same way on every computer all the time. That's just part of the methodology. The last thing we want to hear is that you dislike your new PC because your old one had smiley faces in email or you lost your desktop background picture of your grandkids. Obviously, the real-world moderates this and if Macs are required/desired then IT needs to have a reasonable plan to support them. Losing all your contacts is an absurd things to say to multiple, in-place Mac users. Saying it to one guy who threw his weight around and is the only Mac user in the company is probably reasonable.