the exim.conf file has something about this mine says:
Code:
# If this option is set, then any process that is running as one of the
# listed users may pass a message to Exim and specify the sender's
# address using the "-f" command line option, without Exim's adding a
# "Sender" header.
trusted_users = exim
i bet since mutt uses sendmail command instead of smtp
if you put all users as trusted
trusted_users = exim:user1:user2
maybe exim won't rewrite from: