I got thrown into a situation where I was asked to simply install Exchange 2010. The company has an IT staff, but they left out telling me that what they really wanted was to migrate a company from one e-mail system (POP3) to Exchange 2010, and they had already devised a plan to do it. They have about 150 users spread over a few locations.
Once I was well into it, it was clear that they had more in mind: Their intent is that they already bought a .net domain for Exchange that corresponds to their .com for POP3, and they intend to forward everything from the .com POP3 accounts to the .net Exchange accounts. They never really told me of this plan before I started, and as a sub-contractor, I was not even in on any of the preliminary discussions.
I am 100% sure that Exchange is working properly, and is in place. They are having problems with things like the reply from and other things related to the dual systems. I have my doubts these problems will be solvable, and that they should just make a fast move to Exchange and be done with it. The problem is that I doubt they will do this.
Since they are not far into the actual migration phase, are there any better ways to do this? Especially a better way to run them side-by-side, or should they just get everything prepared, and make one big move (which I am sure they will fight this idea)?
Personally I wouldn't have done the forwarding thing, sucks that you weren't involved with the choosing of that migration phase.
I would have setup a gateway machine that mirrored all incoming email to the appropriate backend server, or even both machines while the migration was taking place.
Making one big move isn't a good idea, there's always something that is missed or that breaks that is unexpected, and when its effecting 150 people instead of 2, it'll be your head.
We last did this between 3 systems (Qmail, Exchange07(?), and Postfix) all with their own incoming and outgoing servers. We wanted to merge them all to Exchange 2010. We setup a postfix server to be the MX receiver for all 3 of those platforms. It received mail for everyone, scanned mail for spam, and then forwarded mail to the appropriate backend server based on a hash table. Clients still sent & received email without noticing any changes, and we slowly got to migrate our clients 1 set at a time. (clients didn't notice any changes until it was their day for upgrade anyway.)