We're migrating mailboxes from Exchg 2003 to Exchg 2010. The Move Mailbox feature will not work for us, so we are manually moving the mailboxes by exporting them from the 2003 to a .pst, deleting the user's mailbox, then creating a new mailbox for the user on the 2010 server, and then importing the .pst into the users mailbox. This works without any error. Most of our mailboxes are still on the 2003 server, although we have moved 3 mailboxes to the 2010 server. Mail is flowing back and forth. Yesterday, we migrated 2 mailboxes via the process above. We can send emails from either of these accts to any other mail acct on the 2003 or 2010 servers, but if we send emails between these two accts we get an NDR. It appeared this was an Outlook cache issue, so on each user's machines we deleted their Outlook profile, renamed any .ost files to .old, and deleted an .N2K files, then created a new Outlook profile...still the same problem.
I can't figure out why this is happening with just these two mailboxes, so far. I'm hessitant to move any other active mailboxes because I don't want this problem to be expanding to any more users.
One other item that I find odd...our mail server(s) accept mail for two different domains...@company1.com and @company2.com. (most front office users have their primary email address as @company1.com, but our IT and administrative users have their primary email address as @company2.com.) The Default Accepted Domain on the mail server is company1.com. The two mailboxes having the problem have primary email addresses as @company2.com (their default reply address)...AS I said above, if the users send each other emails to the @company2.com address, they get an NDR (#550 5.1.1 RESOLVER.ADR.ExRecipNotFound; not found ##), BUT if they send the email with the address of firstname.lastname@example.org, the email is delivered. So, this is making me think it is not an issue with Outlook caching (especially since we tried deleting all of the cached files), but perhaps more an issue with some configuration on the server? Any ideas?