Jerry,
Thanks for checking this. I can't seem to get it to fail - and I tried
1.1.1.1 numerous times - along with several other resolvers - without
any errors. But there's definitely an inexplicable failure rate on
nearly all DNS lookups that's around 1/10th of 1%, or something like
that, where something goes wrong even when there is not anything that's
technically and systematically going wrong anywhere, so hopefully your
lookup was that kind of a rare glitch?
(For this same reason, in my anti-spam system - I check against a few
different servers before assuming that the "no rDNS" answer is valid -
and then my system catches that info - but then I have another system
that just only rechecks those 24/7 to try to remove such negative
caching entries - perchance some of those were short-term malfunctions
that later got fixed. This is very helpful because getting correct
answers for that, in one single query, is NOT 100% reliable - but at the
same time - many malfunctioned systems return very slow answers. So this
system I described provides a 'best of all worlds" situation - it tries
hard to ensure that my system isn't tricked by an individual errant
query, my system isn't bogged down by repeated lookups to zombie-ish dns
servers that are slow to answer, and it quickly self-corrects if a
server was only temporarily down or had temporary issues.)
BTW - for anyone wanting to search their own SMTP logs for this - I
suggest searching on:
Fix reverse DNS
...since that's the phrase that's in both error messages.
Rob McEwen, invaluement
------ Original Message ------
From "Jerry Cloe" <je...@jtcloe.net>
To "mailop@mailop.org" <mailop@mailop.org>; "r...@invaluement.com"
<r...@invaluement.com>
Date 2/20/2025 3:48:41 PM
Subject RE: [mailop] AT&T/Prodogy/Yahoo claims that my sending IP
doesn't have rDNS, except it does!
Tried a few random dns servers, one caught my attn:
; <<>> DiG 9.11.36-RedHat-9.11.36-7.el8 <<>> -x 204.9.77.40 @1.1.1.1
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: SERVFAIL, id: 39575
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 1
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 1232
; EDE: 22 (No Reachable Authority): (time limit exceeded)
;; QUESTION SECTION:
;40.77.9.204.in-addr.arpa. IN PTR
;; Query time: 4852 msec
;; SERVER: 1.1.1.1#53(1.1.1.1)
;; WHEN: Thu Feb 20 14:41:43 CST 2025
;; MSG SIZE rcvd: 78
Pretty much 5 seconds then timed out. Tried a couple times and it did
start working. So something seems wrong somewhere. Every other query I
tried to other resolvers worked.
-----Original message-----
From: Rob McEwen via mailop <mailop@mailop.org>
Sent: Thu 02-20-2025 02:23 pm
Subject: [mailop] AT&T/Prodogy/Yahoo claims that my sending IP doesnât
have rDNS, except it does!
To:mailop@mailop.org;
Starting earlier today (Feb-20-2025) AT&T/Prodogy/Yahoo started
rejection my users' emails due to my sending-IP-address (204.9.77.40)
allegedly not having rDNS, except it does! This is happening to emails
sent to the email addresses hosted at the following domain names:
prodigy.net
bellsouth.net
att.net
And this error is ONLY happening when connecting to either
144.160.159.21 or 144.160.159.22
When my users emails route to their other IPs - 144.160.235.143 and
144.160.235.144 - those are not having any problems. And I'm not
seeing any such "no PTR" or "no rDNS" rejection messages with any
other email systems that my users send to - and I have very good
telemetry on rejections of emails sent by my system.
HERE IS THE ERROR THAT IS BEING RETURNED:
550 5.7.1 Connections not accepted from servers without a valid sender
domain.flph830 Fix reverse DNS for 204.9.77.40
And other times, this error is returned:
451 4.1.8 Client IP address 204.9.77.40 does not resolve.flpd569.Fix
reverse DNS.For more information email postmas...@prodigy.net
But every time I do rDNS lookups on 204.9.77.40, from all various
systems, I consistently get this answered with "mail.invaluement.com"
- so I can't get it to fail. (And it has RCrDNS since this hostname
resolves back to this same IP address)
I asked my IP provider is they are having any issues with rDNS queries
getting answers - and they claim that they're not having any issues.
Then I tried to email support addresses at AT&T/Prodogy/Yahoo, but
they are also returning back with this same error.
Anyone else having this issue? And suggestions? Is there anyone on
this discussion list who is with AT&T/Prodogy/Yahoo and who can assist
this?
Thanks!
Rob McEwen, invaluement
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