Setting From: address for lists dependent on receiver address

[Keld Jørn Simonsen <keld@xxxxxxxxxx>]

I have a problem that for instance on this mutt list, I normally don't
get an indication of how I received this mail in standard mail headers.
And my address for this email list is different from my normal address.
However this address is recorded on my system in a header X-Original-To: 
and such a header can be made available on other systems too.

I am then wondering how to get this info into my From: header.
I don't see ways to get it there via some hook command.
I only see that I could do it via some external program executed in some
backpling shell program. Like in .muttrc:

   set from=`get-original-to $this-mail default@xxxxxxxxxx`

and then get-original-to :

#!/bin/sh
orig=`grep X-Original-To: $1 | head -n 1 | cut -d ' ' -f 2`
# also take care of localhost address without "." :
localaddress=`echo $orig | grep '\\.'`
if [ "$orig" = ""  -o  "$localaddress" = ""  ] ; then 
   orig=$2;
fi
echo $orig


... But I dont see how I can get the current email passed to the shell
in the backpling string. How can that be done?

or is there a better way?

Best regards
keld