Website local, mailserver external

[hendry]

A question: I have more domains running on my latest stable ispCP server (etch). For one of my domains the website is running local, but the mailserver is not Postfix, but an external Exchange server.

Problem is now when somebody is mailing from an other domain to the domain with the exchange server Postfix bouncing the message because the receiving emailaddress is not in the virtual tables.

Is there a setting that I can do to let the ispCP server know that when receiving a message for a user for the Exchange domain it has to be forwarded or is this something to be arranged in the Postfix configuration? If so, how can I do this?