Hi, This might help (I know that the poster in this case is using exchange 2010, but the problem / solution should be the same) http://social.technet.microsoft.com/Forums/en-US/exchange2010/thread/1152448a-de6e-42c4-98d6-16aee71780fc Leif

Whenever we try to forward a user address to an external address in exchange 2007 sp3 rollup 4 we get the following error: set-mailbox Failed Error: Active Directory operation failed on child domain. This error is not retriable. Additional information: The name reference is invalid. This may be caused by replication latency between Active Directory domain controllers. Active directory response: 000020B5: AtrErr: DSID-03152395, #1: 0: 000020B5: DSID-03152395, problem 1005 (CONSTRAINT_ATT_TYPE), data 0, Att 2007e (altRecipient) This only happens on users who are in a child domain. I checked the event log on the exchange server and root domain controller but I see no errors. I did a netdiag and dcdiag on the DC and there no errors on replication.

Hi, I have two methods, you could have a try. 1. Use mail contact to forward email Create a mail contact in the parent domain, and link the email address of the child domain to the contact. 2. Force AD replication, and modify recipient scope. How to Change the Recipient Scope Then you could select the user in child domain when you set email forwarding.