We have just started the planning/design phase for a 2007 to 2010 transition project. We have a limited implementation of Exchange 2007 UM with OCS-hosted phones. Majority of associates have PBX-hosted phones. There is an urgency to move all associates to UM by end of September along with a requirement for features that are only in UM 2010 (e.g. turn on message waiting light). There is an unsubstantiated rumor that we can transition the UM role to 2010 before transitioning other server roles to 2010. All transition documetation says the 'correct' order is to do CAS, HT and Mailbox roles, and then do UM and Edge roles. Does anyone know for certain if UM 2010 depends on other roles being on 2010 first? Thanks!

MWI wont work for Exchange 2007 mailboxes for one. In fact, unless the mailbox is on a 2010 mailbox, the 2010 UM servers will simply redirect the incoming calls to the 2007 UM servers so there is no real advantage to bringing up a 2010 UM server with none of the other 2010 roles installed in the org.

Thank you for the quick response. There are third-party products that provide MWI for 2007 mailboxes. Was hoping to avoid the cost, but can't see us completing a transition all servers to 2010 in under two months.

Some are cheaper than others: http://www.aaronsoftware.com/mwi.html Pretty affordable.

Thanks for the info, Andy. We're contacting the vendor to check it out.