Question : What is the difference between "mydomain" and "mydomain.local"

I had a computer today that was assigned to the domain MYDOMAIN.local, and it would not establish a trust with the SBS server.  I removed it from that domain and attached it to just MYDOMAIN, and it worked.

I've also noticed that we have to set up our mailboxes on MYDOMAIN.local, because MYDOMAIN won't work.

Can someone explain this concept to me?

Answer : What is the difference between "mydomain" and "mydomain.local"

mydomain.local would be the dns domain name
mydomain would be the netbios name - used for computer-to-computer communications

mydomain.local would work for computer-to-computer communications too, but only if the dns server settings are correct

mydomain won't work for email because email has to have dot-something, so it knows where to get routed to (by dns of course)