Entourage - Exchange Account Confg - Help needed.

Here is the scoop:

1) I am able to send and receive email via Outlook exhange account (on win box) no problem.
2) On my Macbook Pro -- I can finally pull email, but I cannot send. I am getting an error message that says the recipients email account is either full or the message is too large.

Clearly, I am not cofinguring something correctly.

Help, Please.

- Andrew