Bernardo Pons:
> On these days where theft of credentials of legitimate e-mail server users
> in order to send spam checking the MAIL FROM: using
> smtpd_reject_unlisted_sender would be a helping Postfix feature.
>
> Perhaps it is a misunderstanding from my side about the actual meaning of
> parameter smtpd_reject_unlisted_sender but if "smtpd_reject_unlisted_sender
> = yes" is present on main.cf...
>
> How is it possible for an user to send an mail from an unknown sender
> addresses neither listed in virtual nor canonical?
It can happen on mail hubs, when an inside system sends mail through
the mail hub, with a sender address that is not properly registered
at the mail hub. Ideally the mail hub would block such mail. For
now, I leave it up to you to decide if you want to fight that battle.
5-10 years ago it certainly would break a lot of things in the real
world.
Wietse
