Alex:
> HI,
>
> On Mon, Feb 19, 2018 at 12:08 PM, Alex <mysqlstud...@gmail.com> wrote:
> > HI,
> >
> > On Mon, Feb 19, 2018 at 11:42 AM, Wietse Venema <wie...@porcupine.org>
> > wrote:
> >> Alex:
> >>> Hi,
> >>> I have a postfix-3.1.4 system with a few hundred people using the
> >>> submission service. One of the accounts was recently compromised, and
> >>> started sending mail as fake users in the same domain. How can I
> >>> prevent this?
> >>
> >> See:
> >> http://www.postfix.org/postconf.5.html#smtpd_sender_login_maps
> >>
> >> And use one of:
> >> http://www.postfix.org/postconf.5.html#reject_sender_login_mismatch
> >> http://www.postfix.org/postconf.5.html#reject_authenticated_sender_login_mismatch
Maybe try the second one instead of the first one?
Wietse
