Unable to Relay

I’m getting ‘Unable to relay’ anytime I try to send email to @”mydomain.com”. I have 2 machines, one is my DC with DNS installed, the other is my Exchange 2000 server. I also have a 3rd machine, which is a client.

I went through several articles in MS. Looked at 323669, which involved recreating a key in the Metabase in IIS.

Also went through 289553, which makes sure my recepient policy includes @”mydomain.com”.

My DNS does have an MX record pointing to my Email server. What else am I missing??