Exchange 2003 Recipient Policy

In our exchange, we have default recipient policy, where we have added 6-7 domains.

I want that for new joinees, whenever I create a mailbox, it should get created with only primary SMTP address. I don’t want to populate other SMTP domain for new joinees. However, the existing account will still have their email address with all these 6-7 domain.

Please let me know how can I achieve this.