Exchange 2000 no mailboxes show up

I just installed Exchange 2000 on Windows 2000 Server.
Went to AD User & Comp-> Selected user, …Exchange Tasks -> Add Mailbox
Successful.
Then went to Exchange -> System Manager
Servers
First Group -> Mailboxes…
and nothing was there? Theycannot connect to Exchange Server in Outlook either.
Any ideas?
I applied SP1.