BB Software :: Get Email And Send To Outside?

I have a client (I am a network consultant) that uses a BB and he can get all his email on it. He is using the BIS service and has had no problems. However when he tries to send, it only delivers to people outside of his local domain. Any of his coworkers do not get his email's. But the even stranger part is that the email's that he sends to his coworkers show up in his sent items box. They just get lost somewhere in the shuffle.

We are using an Exchange Server 2003 and GFI MailEssentials for our SPAM solution.