ispCP, Postfix and Domain Aliases for Mail

[JackD7]

Hiya

I have Debian 6 installed and ispCP Omega 1.0.7 with several Webs.
On Web has several Domains eg.
Dom.de, Dom.eu, Dom.com, Dom.net and Dom.org

For webtraffic it is easy to set an domainalias but how can i do this for Mails?

I only want to manage Mails in Domain Dom.de but i want to get Mail that is adrEssed to all other Domains eg.:

User Smith@Dom.de is a configured Mailbox.
A Mail for Smith@Dom.COM arrives and shouldl be moved to the Mailbox smith@dom.DE.

How can i realize that without Killing my ispCP / Debian / Postfix?

Cheers,

Jack