I currently have multiple domains on my exchange server. There is a user that want's to have two different email address under the same exchange account. She wants to be able to send email from both email addresses. I have setup both email addresses under her profile. She can email from the original (main domain) email address, but when she changes the from address to the other email address she gets an undeliverable message "you can't send messages on behalf of this user. Before someone answers my request, make sure you remember, I only have one exchange account for this user with two email addresses. So there aren't any permission/sharing to allow.