I am getting these errors at random from internal users sending mail to internal users. There is only one server for this organization. All mail is routed through this server (no external relay). The email address they are sending it to is correct. If I turn off cached exchange mode on the client that is getting the error and delete the NK2 saved address from the clients machine- the mail will go through. If I turn cached exchange mode back on- then the error will come back.. sometimes (not necessarily to the same address). I only seem to get these undeliverables to users who have not been with the company for very long. I am thinking that there is a problem with the Global address list not caching correctly. Ideas?