I am doing my first Cross Forest Migration from Exchange 2007 SP3 to Exchange 2010 SP1. I have DNS and all my trusts in place.
My destination forest has some of the users in it already as we are consolidating into an existing domain. So I believe my next steps are to run the ADMT to create the users that do NOT aready exist.
1. Can/Should I run the ADMT again the users that DO already exist to copy over any specific attributes? It is important that the destination user IDs are not altered in such a was as they cannot be used in their current environment. Also, I'd like to COPY them and leave the source User IDs intact and functional. Is this a pipe dream?
Then after I get all the users created:
2. Do I then use the ADMT tool to create the Dist Lists? Or do I do that after the mailboxes move over?
Then I move the mailboxes using new-moverequest shell command
3. Because I want to move these and test them prior to "go-live" is it possible to leave the source mailboxes intact and functional? Basically I only want to COPY the mailboxes, not MOVE them.
I remember with Exchange 2003 to 2010 migrations you had to worry about legacyDNs to avoid NDRs when replying to old messages after a move.
4. Do you have to worry about anything like that when going from Exchange 2007-2010 cross forest? Will my users be able to click on an old internal message, hit reply, and it will go successfully?
I know this is a lot to ask, but I really want to get a level of comfort before proceeding. I'd give 1000 points for this if I could.