Can anyone explain this. We have just migrated a group of mailboxes that contained clients with outlook 2003. (from exchange 2003 sp2 to exchange 2010 sp1) We had prepared to run the profile tool from MS to convert them over. We didn't have to. All of them popped up messages saying the administrator had made changes that required outlook to restart. Restarted and they all worked. The address in the profile had changed and everything seems fine. According to http://technet.microsoft.com/en-us/library/bb124251.aspx This should NOT work. We tested a few more just for kicks and they worked also....... what gives???