From: "Lewis G Rosenthal" <ecs-isp@2rosenthals.com>
Received: from [50.73.8.217] (account lgrosenthal@2rosenthals.com HELO [192.168.200.27])
  by 2rosenthals.com (CommuniGate Pro SMTP 5.4.10)
  with ESMTPSA id 12300505 for ecs-isp@2rosenthals.com; Fri, 21 Feb 2025 14:15:15 -0500
Subject: Re: [eCS-ISP] Anyone else seeing issues today with AT&T and RDNS
 failures when sending?
To: eCS ISP Mailing List <ecs-isp@2rosenthals.com>
References: <list-12280401@2rosenthals.com>
Organization: Rosenthal & Rosenthal, LLC
Message-ID: <67B8D0C1.90806@2rosenthals.com>
Date: Fri, 21 Feb 2025 14:15:13 -0500
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Hi...

On 02/20/25 05:11 pm, Steven Levine wrote:
> In <list-12280221@2rosenthals.com>, on 02/20/25
>     at 03:35 PM, "Lewis G Rosenthal" <ecs-isp@2rosenthals.com> said:
>
> Hi there,
>
>> Today, att.net rejected mail from us to one of their subscribers with a
>> 550  5.7.1 error:
>>    <recipient-address @ att.net>
>>      host ff-ip4-mx-vip1.prodigy.net [144.160.159.21]
>>      SMTP error from remote mail server after MAIL FROM:<sender from the
>> 2rosenthals.com domain>:
>>      550 5.7.1 Connections not accepted from servers without a valid
>> sender domain.flph829 Fix reverse DNS for 50.73.8.217
>> secmgr-va.2rosenthals.com
> I get the same here
>
> ; <<>> DiG 9.11.37 <<>> -x 50.73.8.217
> ;; global options: +cmd
> ;; Got answer:
> ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 42869
> ;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1
>
> ;; OPT PSEUDOSECTION:
> ; EDNS: version: 0, flags:; udp: 512
> ;; QUESTION SECTION:
> ;217.8.73.50.in-addr.arpa.	IN	PTR
>
> ;; ANSWER SECTION:
> 217.8.73.50.in-addr.arpa. 3600	IN	PTR	secmgr-va.2rosenthals.com.
>
> ;; Query time: 246 msec
> ;; SERVER: 8.8.8.8#53(8.8.8.8)
> ;; WHEN: Thu Feb 20 14:12:39 PST 2025
> ;; MSG SIZE  rcvd: 92
>
> A wed search for
>
>   "flph829"
>
> results in a few hints that match your problem, but nothing recent.
>

Yeah, whatever it was (likely that particular server), a subsequent retry 
got the message through. Very odd, though. IAC, it was a good opportunity 
for me to just check to ensure that RDNS was indeed correct, because I never 
really look.

Thanks, and apologies, all, for the noise.

-- 
Lewis
-------------------------------------------------------------
Lewis G Rosenthal, CNA, CLP, CLE, CWTS, EA
Rosenthal & Rosenthal, LLC                www.2rosenthals.com
visit my IT blog                www.2rosenthals.net/wordpress
-------------------------------------------------------------