On Tue, Dec 31, 2019 at 12:20:58AM +0100, Gerben Wierda wrote:
> > since the host has no PTR record you can, just in case, add:
> >
> > reject_unknown_reverse_client_hostname
> >
> > to your smtpd_client_restrictions.
>
> Yes. Hmm, does that come with a big risk for stopping legitimate mail?
> Probably yes given the amount of poorly written smtp clients on web
> sites.
Actually, requiring remote SMTP clients to have a PTR record is
reasonably safe. The less safe version, that is not recommended, is
requiring that PTR record to also forward resolve to the connecting IP
address.
Of course you could be unlucky enough to receive important email from
such clients, but that is not at all common, and such senders would
already be blocked at most SMTP servers on the public Internet.
--
Viktor.
