I've noticed this article over at the Register.co.uk concerning the emergence of MS's Mobile email solution based on Exchange 2003 SP2 and Windows Mobile 5 devices using ActiveSync to communicate.
I was fascinated when I first learnt of the Always-Up-To-Date (AUTD) feature that was in Exchange, and covered that here "Blackberry Killer" Solution back in June 2005, it took me a while to get it even close when I had all the client components at Orange SPV C600 AKU2 by March, but I had to wait until April to finally get it sorted with Want Push email NOW! Mail2web has this running as a Beta service.
It has been a long gestation period but now even my Company is in the process of deploying to Consultants and Sales alike, and it is now only going to get easier with the advent of ISA2006 making it much easier to use Credential based Authentication for the devices. If this is what you are after then maybe these earlier articles may be of some use?
Step-by-Step Guide to Deploying Push email with MSFP enabled WM5 Devices - while working with existing Firewalls like Checkpoint, etc.
Comprehensive guide to Adding ROOT Certificates to WM5 Devices like C600, O2's Xda mini, iMate SP5, HTC Typhoon, HTC Wizard, etc.
Mobile Workshop After dominating the enterprise mobile email space with the BlackBerry solution for so many years, RIM is no longer the only serious game in town. Despite a number of false starts, arch-rival Microsoft now appears to have closed the gap, at least in terms of forward looking commitment.
In a recent Reg Reader poll, the number of enterprise respondents citing native MS Exchange with ActiveSync as their strategic mobile email platform was almost identical to the number committed to RIM Blackberry.

Furthermore, when we look at the mid-market and SMB/SOHO situation, we see a pattern of Microsoft dominance emerging – not anywhere near the level we see with PCs, but clearly heading in that direction.
