[Exim] transparent forward

hi,

I get some mail from a pop3 account with fetchmail.
in the .forward I have another mail addr,
so each mail get forwarded to another addr off site.
But some mail get frozen and the forwarded addr get a from header with
my email addr, where i would like it to be the original addr

how can i make this transparent ?
(ie hiding all this process, masquarading as if the mail when directly
from the original sender, not by the pop3 account and my computer,
execept for the header useless to users like Received:)

thanks for you help


edouard