A migration will give you a number of advantages. You won't lose SID
history and can preserve security information on file shares (can use
Robocopy to move data to a new server and copy the permissions). You
won't need to export mailboxes, you can move them instead. Your users
will also be able to reply to old emails from within the company.
Generally speaking a migration is the preferred method unless your
existing domain has problems with AD.
If you do a migration, you will have little impact on production, you
can bring the new server online during the week and reserve final steps
for the weekend so you don't lose your weekend.
If you go the route you are planning, you will need to export mailboxes
and then import the PST files using PowerShell. (no ExMerge on Exchange
2007). Refer to the thread "Moving pst files from SBS 2003 to 2008"
posted 7/2 in this forum by Bobby Janow for my comments on how to do
that.
Note that users will not be able to reply to old emails from within the
company because those mails will have been sent from a different
account than the users will currently be using. You avoid this problem
with the migration.
If you have mailboxes over 2.1 GB then you will have problems with your
export using ExMerge on the old system because ExMerge doesn't support
Unicode PST files. (PowerSHell does).
I recommend you follow the steps in this technet article:
http://technet.microsoft.com/en-us/l...34(WS.10).aspx
Hope that helps,
Mark D. MacLachlan