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Re: [ietf-smtp] IETF Policy on dogfood consumption or avoidance - SMTP version

2019-12-16 16:53:16
On 2019-12-16 2:27 p.m., Viktor Dukhovni wrote:
Correct, checking whether the FQDN exists (and even more so resolves to
the client IP) has too high a false positive rate.

But why the rejection of a IP-literal if it won't even check if the FQDN
is even exist or if it matches any of the IPs or even the SPF.  I don't get it.
That's easy, ... a sufficiently low false-positive rate allows this
check to weed some junk.  That's all there to it.

"Real" inter-domain relays use FQDNs (whether valid or not), almost
none use address literals.

Mind you there are also reasonably good curated lists of HELO name
regexp patterns, that also have low FP rates, and do a decent job
at stopping lots of spam.  These mostly match PTR records of various
dynamic IP ranges that haven't made into the SpamHaus PBL or similar.

Frankly, it simply points to professionalism, is the operator of the sending platform informed enough to use a proper FQDN, and often that is enough to make some operators consider email arriving as less trust worthy.

In a day and age where operators already go far beyond simple configuration items (eg some refusing to consider email from a domain without SPF records as more spammy) we should 'up our game'.

Having said that, I don't think the RFC's are the right place to enforce that you NEED a FQDN yet. Just expect it will probably end up in a spam folder or rejected, without a white list ;)

We all now pretty well universally reject all email unless the IP sending it has a PTR record, doesn't mean the RFC should say we HAVE to have a PTR to send email. (That would probably be a better starting point).

However, once we go down that slippery slope, it will affect more and more legacy and legitimate senders.

Let the operators decide what they will and will not accept, still seems the logical conclusion.

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