Setting up new email address on server

Recently my company established a new division and wanted to set up a new email address to accompany it. So I went into the active directory on our server and set up the new email address for the necessary users. I also set up the new address on the exchange system manager. When I send test emails internally through outlook, they go through fine. However, when email is sent to these new addresses externally, it gets bounced back.

I think the problem is that a new MX record has to be created on the DNS manager. However, I’m not really sure of the procedure. Any help/advice is appreciated.

Thanks

Thanks