No reverse DNS

[David-J-Taylor]

I'm getting emails returned sometimes when mailing to groups.io.  This does not happen when I use a different mail sender, just blueyonder email.

Diagnostic-Code: smtp; 500 Invalid request, no reverse DNS for 84.116.50.34
Diagnostic-Code: smtp; 500 Invalid request, no reverse DNS for 84.116.50.35
Diagnostic-Code: smtp; 500 Invalid request, no reverse DNS for 84.116.50.37
Diagnostic-Code: smtp; 500 Invalid request, no reverse DNS for 84.116.50.41

So should blueyonder/virginmedia be fixing this by providing the appropriate reverse DNS data for all their outbound mail servers, or is the issue somewhere else like at groups.io?  Whois seems happy with the IP addresses.

Thanks,
David

[coenoby · Accepted solution]

---

@David-J-Taylor wrote:

So should blueyonder/virginmedia be fixing this by providing the appropriate reverse DNS data for all their outbound mail servers, or is the issue somewhere else like at groups.io? 

---

That's very strange. I have just done a reverse DNS check using this checker https://mxtoolbox.com/ReverseLookup for all those mail servers and they all seem to be coming up ok. For example

Are you still getting that error and if so is it from just one recipient or all recipient?

If the mail servers that VM use did not have a valid reverse DNS then the forum would be going mad with loads of people complaining that they could not send VM emails.

Coenoby

[David-J-Taylor]

Yes, I checked here and saw reverse DNS appeared OK.  It's just groups.io, but only an VM servers.

[coenoby]

---

@David-J-Taylor wrote:

It's just groups.io, but only an VM servers.

---

Thanks for coming back. I have no experience of using groups.io but a quick search revealed that they may have previous form with reporting apparently spurious DNS errors, see here: https://groups.io/g/GroupManagersForum/topic/unable_to_post_to_my_group 

Admittedly that was a few years ago and I am also not entirely sure that post is entirely relevant to your experience.

Scroll to the bottom of that page and you will see the comment   "This has cropped up from time to time before, but I don't recall if there was a resolution".

They also suggest the best advice is "to use a different email service." You said in your first post that you don't get the problem when using your other email service so I think that would be a good work around.

You could contact groups.io, they may have an answer or at the very least give some information as to why the VM servers are failing group.io's checks when no-one else seems to be reporting any issues with VM's setup.

That would at least give the technical VM teams something concrete to work with.

One of the VM Forum Team (VM staff) will be contacting you via this thread hopefully today bit all they can do is pass it on to the relevant technical team. My feeling is that the VM technical team will say they cannot see an issue on their side. 

In my opinion a bit more clarification from groups.io would definitely be helpful.

Coenoby

[David-J-Taylor]

Yds, well "please pass to mail team" was my first request to VM who said they have no way of contacting the team, hence the present circus go-around!  I will try to attach a full error 500 response  here.  Oh, there doesn't seem to be an attach, so inline it is.

Well, it seems it isn't valid HTML - damn it it's text!  Give up.
Cheers,

David

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======================================================================
Subject: PP-log-report-from-Edinburgh-2023/09/13
Plane Plotter with the Beast report from David Taylor, Edinburgh 2023/09/13    Created with [removed] report toolkit V2.3.0 .. download: https://www.satsignal.eu/software/MakePlanePlotterReport.zip .. support: https://groups.io/g/SatSignal   Times are UTC   Hex    Callsign   Reg     Type       
======================================================================

The following addresses failed:


  mode-s-logs@mode-s.groups.io
    host lb01.groups.io [45.79.81.153]
    SMTP error from remote mail server after RCPT TO:<mode-s-logs@mode-s.groups.io>:
    500 Invalid request, no reverse DNS for 84.116.50.34

Reporting-MTA: dns; csmtpq3-prd-nl1-vmo.edge.unified.services

Action: failed
Final-Recipient: rfc822;mode-s-logs@mode-s.groups.io
Status: 5.0.0
Remote-MTA: dns; lb01.groups.io
Diagnostic-Code: smtp; 500 Invalid request, no reverse DNS for 84.116.50.34

Return-path: 
Received: from csmtp2-prd-nl1-vmo.nl1.unified.services ([100.107.82.134] helo=csmtp2-prd-nl1-vmo.edge.unified.services)
	by csmtpq3-prd-nl1-vmo.edge.unified.services with esmtps  (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384
	(Exim 4.93)
	(envelope-from 
	id 1qgbfH-005l8L-DK
	for mode-s-logs@mode-s.groups.io; Thu, 14 Sep 2023 04:01:07 +0200
Received: from Penguin ([94.173.109.94])
	by csmtp2-prd-nl1-vmo.edge.unified.services with ESMTP
	id gbfGq9XmJELBSgbfGqEl8V; Thu, 14 Sep 2023 04:01:06 +0200
X-SourceIP: 94.173.109.94
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Date: Thu, 14 Sep 2023 03:01:06 +0100
From: [removed] @blueyonder.co.uk
To: mode-s-logs@mode-S.groups.io, david-taylor@blueyonder.co.uk
X-Mailer: Blat v2.6.2 w/GSS encryption, a Win32 SMTP/NNTP mailer http://www.blat.net
Message-ID: <01d9e6af$Blat.v2.6.2$5276b3b0$8918f8c52548@blueyonder.co.uk>
Subject: PP-log-report-from-Edinburgh-2023/09/13
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[coenoby]

@David-J-Taylor 

I replied to you earlier this morning but my post seems to have disappeared.

I have notified the forum moderators to redact your email address from the post. It's a bad idea to post your email address on an open forum😉

I would hope that the forum team will give you a better response then you have had from VM so far. As long as you are a VM broadband customer they  can help  you.

Thanks for posting the full error message. Sadly,  error messages only quote the error they don't explain what checking the recipient has done in background to arrive at that error. The IP address of the VM mail servers do give a  reverse DNS so why are groups.io reporting there is no reverse DNS?

I am wondering if the issue is not that there is no reverse DNS but groups.io do not like the DNS that it comes up with. As I said earlier some clarification from groups.io might be helpful.

Coenoby

[David-J-Taylor]

Let's see what happens.  Thanks for commenting.

Cheers,
David

[ravenstar68]

@David-J-Taylor I've done my own reverse DNS lookup on each of the IP addresses in the original post

(base) timothydutton@Timothys-MacBook-Air ~ % dig +short -x 84.116.50.34
csmtpq3-prd-nl1-vmo.edge.unified.services.
(base) timothydutton@Timothys-MacBook-Air ~ % dig +short -x 84.116.50.35
csmtpq1-prd-nl1-vmo.edge.unified.services.
(base) timothydutton@Timothys-MacBook-Air ~ % dig +short -x 84.116.50.37
csmtpq2-prd-nl1-vmo.edge.unified.services.
(base) timothydutton@Timothys-MacBook-Air ~ % dig +short -x 84.116.50.41
csmtpq4-prd-nl1-vmo.edge.unified.services.

As you can see all four have a valid reverse DNS.  I also sent a mail to check the point where it hits my mail servers

Received: from csmtpq4-prd-nl1-vmo.edge.unified.services (csmtpq4-prd-nl1-vmo.edge.unified.services [84.116.50.41])

The header tells me that my server also found a valid reverse DNS and that it matches the name provided by the mail server at the time of connection.

The problem looks to be on the receiving end, they need to work out why their DNS resolvers aren't finding a valid reverse lookup.

It's not the first time I've seen this, but the last time was in reverse where VM's DNS servers on the mail platform were doing the same thing with a a specific set of authoritative servers ran by a hosting company.

Tim

[Kain_W]

Hi David-J-Taylor,

Thanks for your post and welcome back to the community.

Sincere apologies for any issues faced with your email, just so we can gain further clarification with the emails that you are sending, are they being sent by a 3rd party client or from MyVM?

Let us know,

[ravenstar68]

@Kain_W I'm going to answer on behalf of the affected customer here.

They're being sent from one of the Virgin Media email domains via Virgin Media's outbound mail servers

This is not a problem with the customers email setup, the IP addresses in the original post are the outbound mail servers from Virgin Media's email platform itself.

In the interests of fixing this for the customer the mail tea might want to reach out to the postmaster on the receiving side so that they can look into this issue.  The receiving party might not be aware of the problem on their side.

Tim