OWA won’t let other domains in

Exch 5.5 w/ SP3, NT4.0
I just moved my OWA from a separate server to the exchange server itself. Now all of the sudden only users that are part of the domain that the server is in can get in.
Log on Locally & Access computer from network permissions are granted to Everyone. All of the basics seem to be covered (I think?).
Everyone gets their mail fine. This is strictly an OWA problem.