[exim] Forwarding certain mails to other SMTP server & chang…

First of all, thank you for reading my message.

This is the first time I'm setting up an Exim mailserver without the use of
Direct Admin to learn a bit more about it. So far it's working great, but
I'm stuck a bit at the configuration differences between inside and outside
our lan environment.

I want the server to accept mail from a few domains, one being for internal
mail, 2 others for external which deliver into the internal mail mailboxes.

But not all incomming e-mails from our internal *.lan clients are supposed
to go to ra.lan to be delivered. Some outside mails are also send to that
server, but they have to be delivered to another smtp server outside our
local .lan network. Furthermore, when this happens we usually have a wrong
FROM that's rather internally based, that should be changed to reflect the
outside domain instead of the inside one before it's relayed to the other
SMTP server.

I've got no clue on how to accomplish something like this. Although I can
set up a simple Exim server with my eyes closed now, I could use a few kicks
into the right direction for this problem. The mailserver currently is a
standard exim 4.50 that comes with Debian Sarge (unstable).

--
With kind regards,
Sebastian Berm