Question : Undeliverable Email with Exchange 2007

A while back we upgraded from Exchange 2003 SBS to Exchange 2007.  During the misery we discovered that besides the two versions being incompatible, there is a address problem which we cannot resolve on our customers end.  We get a lot of undeliverable because of the "First Administrative Group" in the addresses of some of the emails.  

IMCEAEX_O=MYD_OU=First+20administrative+20group_cn=Recipients_cn=amar@mydomain.com  #550 5.1.1 RESOLVER.ADR.ExRecipNotFound; not found ##

The problem is that [email protected] is a valid email address.  How do I tell exchange that addresses that come in with "First Administrative Group" are ok and actually should go to the Recipients_cn if valid, which in this case it is.

Thanks.

Answer : Undeliverable Email with Exchange 2007

you need to update the mailbox(es) with an X500 address that matches the NDR