Ever since Microsoft invented that "frequently used email cache" in Outlook, migrating users from one server to another has become problematic. Once a user is moved, other people using Outlook 2003+ can no longer use the cached email information that is stored in the .nk2 file. When messages are sent using those entries, the sender receives an NDR. Instead, we have been coaching people to select the user from the GAL.
We are currently planning a migration from Exchange 2003 to 2007 which will entail moving all of our users in North America. I wanted to see if anyone had some recommendations on how to handle this situation because forcing people to temporarily stop using this autofill feature will not go over all that well.
What are other Exchange administrators doing about this?