[exim] forward single users to another mta

Hello all,

I try to find a way to forward E-Mails per User to another MTA (like a
transport map in postfix).
The reason for this is, that I need to migrate to another Server (exchange)
and I can't move all Users at once.
What I would like to implement is the following:
1. exim Server receives the mail for mydomain.com
2. if the recipient is whatever@??? the mail should be forwarded to
exchange
3. if the recipient is somethingelse@??? it should be delivered
local.

Is this possible? If yes, what needs to be configured?

Regards,
Stefan

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Stefan Lubitz
Head of IT
System Administrator
___________________________________________________________________________
MACKEVISION
Medien Design GmbH, Stuttgart
Forststraße 7
D - 70174 Stuttgart