Microsoft 2007 Exchange migration
We are in the middle of our in situ 2007 transition trying to use the existing 2003 environment in tandem with the 2007 architecture. It is, supposedly, a supported type of transition where things just intelligently balance themselves depending on where your mailbox is. For the most part is looks like it wants to work, but there are a couple of limitations that we ran in to (or perhaps just isolated bugs) that prevent us from doing a graceful transition.
Problem 1 is that 2007 front end (or CAS as they call it now) works flawlessly with webmail, webdav and owa for both 2007 and 2003 based mailboxes, but it only works properly for ActiveSync on 2007 mailboxes and fails to proxy correctly for 2003 mailboxes. That is obviously a no-starter for all of our mobile users. So we have to scratch the CAS box flip for now.
Problem 2 is that the 2003 front end can not handle 2007 mailboxes because of the switch from /exchange to /ews. So we have to scratch using the 2003 front end for 2007 users.
Problem 3 is we are not using a reverse proxy so I can not intelligently look at the client coming in and direct them to the appropriate server.
In retrospect, the reverse proxy would have been the better idea but it also added another component to the architecture that we were not planning on time or money wise. We had always held the door open for the potential to use one, just not as part of the upgrade. The admin inside of me wants to fix the ActiveSync problem on the 2007 front end and then all will be right in the world, but the logical side of me that has done this type of change hundreds of times knows that if I go down that rabbit hole I will not be able to successfully time-box the work. Things get a little to tangential when you are troubleshooting something so specific.
I have a feeling that we are just going to need to do the full monty 2007 migration and take about 10 hours of downtime in the process to get this thing working, but I keep holding out for another option (like a IIS based proxy for the /Microsoft-Server-Activesync service where I can just proxy all requests to the 2003 FE)… but we are running out of time.
I will update with the final result, in case anyone searching happens to come across this. I have not been able to find -anything- on the intarweb that indicates this problem has happened on a large scale or with people who actually post to forums instead of calling M$.
