Problem with routing email offsite

[pstanbra]

HI
I have dns for a domain externally.
BUT - i've also added the domain internally in ispcp so I can change the external dns to internal ispcp dns and reduce downtime .

BUT I HAVE A PROBLEM.

When I try to send an email to user@domain, the user does not receive the mail. I checked in the log and see this error.

User unknown in virtual mailbox table


okay so, it knows it has the domain internally and tries to route to a local mailbox. I have changed the domain info in bind and changed MX to the external email server. Still the same.

What am I missing.