Hi,We are having trouble on our domain with user accounts being unable to send their e-mail. We receive "You Do Not have Permission to Send on Behalf of the User" as a responce. The permissions are still visible on the mail server, but the account is not allowed access. It should be noted that not all users are receiving this error, but about two weeks ago many users suddenly started to get this problem.We are running Exchange 2003 (Version: 6.5.7638.1). Our domain structure is a group of nine individual domains conntected by trusts. The mail server is in it's own domain and each of the users has their own account on the local domain. The users are given permissions to access the "external" domain e-mail. We are planning to move away from the current domain structure, but that won't be for several months.Thanks for any help you can give.

Try this http://msexchangeteam.com/archive/2005/01/07/348596.aspx .Raj