I wrote:
> > From: Mike Brown <brown@???>
>
> > 504 <brown@mrvideo>: Sender address rejected:
> > need fully-qualified address
>
> > Return-path: <brown@mrvideo>
>
> > From: Mike Brown <brown@???>
>
> > User-Agent: Mutt/1.5.17 (2007-11-01)
>
> You need in Muttrc or ~/.muttrc :
>
> set envelope_from=yes
> #
> # Name: envelope_from
> # Type: boolean
> # Default: no
> #
> #
> # When set, mutt will try to derive the message's envelope
> # sender from the "From:" header. Note that this information is passed
> # to sendmail command using the "-f" command line switch, so don't set this
> # option if you are using that switch in $sendmail yourself,
> # or if the sendmail on your machine doesn't support that command
> # line switch.
And if you run Exim on the same machine as Mutt
then in the beginning of Exim config:
untrusted_set_sender = *