We upgraded our Exchange 2003 on Win2003 to Exchange 2010 on Win2008 R2 recently. The X03 server has not been demoted yet, but is currently turned off. The issue I am having is that one particular user (USER 1) cannot email another particular user (USER 2) whose name shows up in the global address list. User 1 can see and select User 2 in the global list, but gets a non-delivery reply.
Note that this only happens when User 1 tries from inside the network. From OWA, User 1can email User 2 fine. Note also that User 2 can send emails to User 1 from any location.
The only possible cause I can think of is that when moving mailboxes from 2003 to 2010, User 2's mailbox would not move. I kept getting errors. I finally downloaded its messages to local folders and deleted the account from active directory. I then recreated the account, established a mailbox on the 2010 server, and reloaded the saved messages from the local folders. This procedure worked well, but I'm wondering if the User 2 entry in User 1's Global address list is actually tied to the old account?
The strange part is User 2 does not seem to be having any difficulty receiving email from anybody else (at least I am not aware of any difficulties.)
p.s. This is a school and I am responsible for a few classes. I will try to monitor this, but may not be able to respond as promptly as I would like.