On 2020-09-24 12:07, Rick Moen wrote:

> I've had no problems _without_ DMARC/DKIM (but with a strongly
> asserted SPF record). Have been operating home *ix SMTP smarthosts on
> static IP with matching rDNS, and maintaining a clean, high-reputation
> system since the 1980s.
>
> I've tried to always have rDNS always match exactly my main mail
> server's primary identity, though it has several valid alternate
> public identities (uncle-enzo.linuxmafia.com, hugin.imat.com,
> unixmercenary.net) that in my experience _also_ enjoy high reputation,
> despite A-to-PTR mismatch.
>
> Basically, in my experience, some operators may be assigning a _very
> small_ spamicity score to 'rDNS exists but doesn't match': I cannot
> really tell. What's clear is that 'IP lacks rDNS' is (rightfully)
> penalised, given RFC mandate for same and its usefulness as an
> antispam heuristic.

FWIW, I check for DNS round trip and passing SPF, and I reject (but not
blackhole) when both fail.

--
Ian