EXCHANGE 2000: Child domains and users accounts

I have a Lab setup. Root domain, ABC.int with an DC that has exchange 2k. All users in ABC.int domain has mail settings, and mail works fine.
I have a child domain abc.ABC.int
All the user accounts for abc.ABC.int are in this domain.
Replication is working fine, DNS is working, WINS is working.
I want to point the users in abc.ABC.int to the exchange server in ABC.int but when i create accounts in this domain, there is no option to create a mail box… what am i missing? (probably simple huh)
THANK YOU
Wok