[rwjblue]

I think that the problem is that zimbra is acting as the authoritative server for the domain, and since it does not have a record of the exchange addresses it thinks they are invalid.

I have configured the domain on zimbra to use Active Directory for authentication, but not for the GAL. Should I try setting the GAL mode to "Both"?

If it isn't possible I can setup a sub-domain for my zimbra users, but I don't really want to have to do that...

Thanks again,

Robert Jackson