Re: [exim] rewrite From: with MAIL FROM:

Some more info how to do it please - I'm really not good at configuring
exim.

Reason for rewriting From: header inside email with MAIL FROM: is anti mail
sender spoof. MAIL FROM: gets verified in smtp session, from: header does
not. Gmail does such rewriting. Other servers do not and you can send email
using their service while signing as any sender. I realize that such rewrite
is not with accordance with rfc-s but many things can't be those time when
fighting abusers.