Postfix Rewrite domain only after transport process

we have a particular situation were we have like 2 domains

lets say example.com and test.com

The first domain has some address that go trough the postfix gateway and in the transport, if the address match, its going to another smtp server, at this point no big deal

but now, the thing is that if the email does not match any of the transport file
i would be able at that point…. to rewrite the domain from (.*)@example.com to [email protected]
and then reprocess it in the transport to send it to another smtp server

any idea how to achieve that ?