According to the kb article (assuming you are following the first method described), exchange should be non-authoritative for the shared domain. It also says that exchange must be authoritative for the primary smtp address on the default recipient policy. So, you cannot make exchange non-authoritative for the smtp address on the default recipient policy.
Looks like you should create a new recipient pollicy (with the smtp address of the domain you want to share) and change the default recipient policy to have a new address (like exchange.domain.com).
Also, it sounds like (since exchange is sending the NDR) exchange is authoritative for the shared domain. Make sure that "This Exchange Organization is responsible for all mail delivery to this address" is not checked in the recipient policy properties. |