A number of people would wonder if Asterisk is supported as a gateway for the Microsoft Exchange Server 2007 with the Unified Messaging role.
Well, as far as Exchange Server goes, Asterisk/Exchange UM is not a supported configuration but that doesn't mean "it cannot work". Microsoft does have a different view of what the term supported means; and if you want to learn more, you can find a list of what's been confirmed to interop with Exchange Server 2007 on the following link:
Telephony Advisor for Exchange Server 2007
Folks such as Ryan Newington Accessing Exchange 2007 Unified Messaging have demonstrated great techniques on making these 2 products connect and "talk to each other" using a proxy server in between.
Ryan has used SipX in his tutorial and I must say it's a successfull implementation provided you follow his instructions steps by steps and obviously have some knowledge on SIP and RTP, etc.
But some may ask why is it so difficult to configure Asterisk and Exchange UM together? Well, the answer is simple and complexe..... but we prefer the simple portion of it. The answer is as simple as "they just speak in different languages"; thus "the need for a interpretor"
Asterisk talks SIP using UDP while Exchange (and most of commercial-grade SIP servers) speaks SIP but over TCP.
However, since Asterisk version 1.4, talks have been rising to make it talk SIP over TCP as well; after all, when Mark Spencer came up with the idea of Asterisk back in the late 90', I believe, he thought of his creation finding no such boundary but integrate smoothly with already existent technology, network, etc.
An intern at Digium started to "teach" Asterisk the "SIP via TCP language" and I can say, they've done a great job as Asterisk 1.6 (currently still beta) can talk TCP.
That's good news, specially for those who loved Ryan's work (and others) but couldn't buy the idea of having an extra box sit in between.
We've done some work on it and can configure it work except a couple of issues here and there. [now fully works as we were able to clear all the issues we could think of]
Next time, we'll be showing you steps by steps how to set up a successful configuration of Asterisk with Exchange Server 2007 UM.
Until then, y'all have a great week end!