If your company is preparing for Exchange 2007 deployment and is considering or running Asterisk open-source IP telephony, there is a way to make the two systems coexist within the same organization.
On his blog, programmer Alan Dutton provides
If someone dials in and connects to Asterisk, and then punches 666666, they'll be forwarded to the Exchange 2007 auto-attendant. If they dial 55, they'll be forwarded to the Exchange 2007 Subscription.
The exact number to dial for each is arbitrary, and I believe it can be changed as long as it doesn't conflict with other commands. (I suspect the author's choice of 666666 is a joke.)
According to Alan Dutton, a few things still don't work yet. For one, caller ID is not passed from SIPX to Exchange Server, so voice messages forwarded in this manner are tagged as "anonymous." Additionally, the instructions for dialing out from Exchange Server are included in the linked article, but have not been tested by the author yet.
About the author: Serdar Yegulalp is editor of Windows Insight, a newsletter devoted to hints, tips, tricks, news and goodies for all flavors of Windows users.
There is a much more detailed description of how to access Exchange 2007 Unified Messaging features using the open-source tools Asterisk, Trixbox and sipX.
I read this article and thought you might be interested in the instructions I wrote about configuring Asterisk and sipX to work with Exchange Server. I built upon Alan's post, clarified a few things, and also fixed a few problems with his instructions.
This tip originally appeared on SearchExchange.com. This was first published in January 2008
This was first published in January 2008