[exim] exim behind a proxy

Hi exim-users.

I got a problem with the configuration of my exim.
But from the start:
I'm behind a proxy-server with my PC, and I want to send my mails without
using a webinterface.
I want to fetch my mails via fetchmail (it works), edit them with mutt,
and then send then via exim.
So, but I didn't find a hint in the documentation, how to edit the
exim.conf, that it will work.
I add the IP of my mailserver in the "Routers configuration" part of the
exim.conf, but the only thing that happens is, that it seems the mails are
sent, but I got an information everyday, that there are still some mails,
that could not be sent.
I think, that I have to add the information of the proxy-server somewhere
in the exim.conf, but I don't know if it is the right solution, and where
I have to add these lines :)

Thanks for your help

Best regards

German