I have a customer that has SBS 2003, they have 2 external domains (lets call them domain1.com and domain2.com) previously they had both domains MX records pointing to the exchange server. Recently domain2.com has been moved over to google apps and the mx records modified to reflect that. Everything works fine and dandy except the users that are on domain1.com cannot send email to the 1 user on domain2.com. I think this is because exchange still thinks he mailbox is internal and is delivering it there. SInce I figured that was the issue I deleted his old mailbox since all the mail has been moved to the new google apps mailbox hoping that would tell exchange this mailbox is no longer here. Well that is what it did, now they get a NDR saying his mailbox does not exist. How do I tell exchange to send this message out to the new google apps mailbox?