Migrating from Exchange 5.5 to Exchange 2010

Solution 1:

In short, there is no way I would start from scratch....it would probably end up being more work in the long run. You will also have too many little issues, like things with free/busy data, not being right. Other things, like when people reply to existing e-mails, won't work. Depending on the attitudes and political power of the users, you will potentially have a lot of grumbling. That said, I have done the migration from 5.5 to 2003 many times, and 2003 to 2007/2010 many times, so it is not a big deal to me.

You might be better off trying to force your company to hire an outside consultant to do at least portions of the migration...like 5.5 to 2003 especially. Maybe you can do the second half? Or all of it even. After all, they are the ones, who put it off, and now it is already less familiar technology.