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sending emails deffered

HI

We are an ESP and on 1 of our shared hosting platforms, email is been deferred (greylisted) and also receiving too many sessions error (see log from this morning below).

Please could I ask why this may be happening and who to contact to resolve this issue on 1 of our servers.  We currently have overcome this short term by relaying through another 1 of our servers.

We have extremely good reputation, not listed on any RBLs, blacklists etc (which we monitor), and hold all FBL with all major mail providers who run FBL, with no issues sending email to any of the major mail providers, as we do not allow spam sending/mass mail, and take very quick actions to stop any violations.

I am not sure what details you would need, and do not want to appear to be advertising, so if you could let me know who to email details to, and I will do so.

I do hope this can be resolved quickly

Many thanks

John

2017-02-19 09:34:04.335212500 delivery 10427: deferral: Connected_to_212.54.58.11_but_greeting_failed./Remote_host_said:_421_mx7.mnd.ukmail.iss.as9143.net_bizsmtp_Too_many_simultaneous_sessions/?
2017-02-19 09:34:04.334984500 status: local 0/10 remote 1/25
2017-02-19 09:34:04.334981500 delivery 10428: deferral: Connected_to_212.54.58.11_but_greeting_failed./Remote_host_said:_421_mx7.mnd.ukmail.iss.as9143.net_bizsmtp_Too_many_simultaneous_sessions/?
2017-02-19 09:33:52.173745500 status: local 0/10 remote 2/25
2017-02-19 09:33:52.173744500 starting delivery 10428: msg 4982916 to remote ****removed****@virginmedia.com
2017-02-19 09:33:52.173722500 status: local 0/10 remote 1/25
2017-02-19 09:33:52.173720500 starting delivery 10427: msg 4982654 to remote ****removed****@virginmedia.com

 

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Message 2 of 15
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Re: sending emails deffered

Hi John

Bear in mind this is primarily a Community Help and Support Forum.

I'll ask that the @ModTeam flag this for the attention of the Forum Team as normally it can take them up to 7 days or more to respond to posts.

Unfortunately the Forum Team do not work on a Sunday so the earliest this is likely to be picked up is tomorrow.

Based on your logs it does look as if Virgin Media's graylisting solution is getting out of hand again. Smiley Sad  This would appear to tie in with other reports of mails such as Amazon password reset mails not being received.

There's another thread where another IT admin is reporting mails being blocked as spam, but they've not provided any logs.  As Virgin changed the default spam filter settings from reject to deliver mails to the spam folders - outright rejections should be much reduced, so I suspect that too is down to the graylisting as well. Smiley Sad

Tim

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Message 3 of 15
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Re: sending emails deffered

Hi Tim

Many thanks, much appreciated thank you

I thought it maybe as you posted, it started last week but we allowed 7 days to see if it was resolved

Once again, many thanks

John
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Message 4 of 15
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Re: sending emails deffered

Hi John,

Please accept my sincere apologies for this. We have had a few other reports of this particular issue and Postmaster, along with Liberty Global email engineers, are investigating. 

I'd like to add your data to the investigation but do require a little more information from you so have requested this privately via PM (purple envelope icon, top right of page). As soon as your reply is received I'll get this raised for attention.

Many thanks,


Jen
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Message 5 of 15
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Re: sending emails deffered

Hi John,

Thank you for that wealth of information, much appreciated Smiley Happy

Interestingly a domain check reveals a missing DMARC record which shouldn't result in a flat delivery refusal (though a refusal would be in order if there were no SPF records) so in that respect I see a distinct link between your issue and the others I've flagged.

Anyhow I have escalated this to Postmaster for you, ref: F005094933, and I'll get back in touch as soon as we have an update on this.

Many thanks for your co-operation and patience in the meantime,


Jen
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Message 6 of 15
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Re: sending emails deffered


Jen_A wrote:

(though a refusal would be in order if there were no SPF records)


No, it wouldn't, there's no requirement for a domain to have an SPF record, it's a recommendation - in order that receiving mail servers can identify if mail is coming from a server authorised to deliver mail for that domain.

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Message 7 of 15
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Re: sending emails deffered

Hi Ravenstar68

Many thanks

I believe whilst SPF and DKIM/DK are not mandatory to have, email is scored better if these records exist. As Jen stated, also DMARC would give a better score, when determining if email is authentic, sent from a authorised mail platform/sender, but also, some also check sender reputation and/or domain reputation, which again, is scored.

We have full SPF, DKIM/DK records setup, checked for correctness and are usually 2048 in key length (some platforms cannot handle 4096 key lengths, and therefore fail), are not listed in any RBL/SRBL and reputation is between 90 - 100 % (as this is fluid).

I have not heard anything as yet as to if we can resume normal email sending on this one server, so we still have relaying in place.

I would appreciate an update if this is posssible please

Many thanks

John
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Message 8 of 15
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Re: sending emails deffered

@d2d4j

You would be correct apart from one problem, SPF records can't be checked at the point the connection is rejected.  DMARC definitely can't

My evidence for this is in your logs

2017-02-19 09:34:04.335212500 delivery 10427: deferral: Connected_to_212.54.58.11_but_greeting_failed./Remote_host_said:_421_mx7.mnd.ukmail.iss.as9143.net_bizsmtp_Too_many_simultaneous_sessions/?
2017-02-19 09:34:04.334984500 status: local 0/10 remote 1/25

Greeting failed would suggest that either the Virgin Media server rejected the connection before or on receipt of the HELO/EHLO message from your server (more likely the former).

SPF relies on the server sending the envelope sender address in the mail from: command.  I'm assuming you understand the anatomy of an email send.

DMARC goes further and uses the From: address, which of course, is sent in the DATA portion of the email, and can actually be different to the envelope sender.

So at the point the mail server is sending it's 421 error - SPF and DMARC are not a consideration.

Tim

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Message 9 of 15
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Re: sending emails deffered

Hi Tim

Many thanks

If you have a quick look at spamdyke, you will this can be used to check at the point of contact, the checks been made at that point against the ip reputation, IP address and sending server domain for spf. It depends how it has been setup

I understand your point though, over the email sender domain been checked after initial connection

The above works by denial of the sending server if it's known to be poor, and thereby all emails originating are spam. However, it also checks rbl/srbl, which most receiving servers can do, but the checks are initially only against the sending server only

I'm sorry if I was not clear or caused confusion

Many thanks

John
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Message 10 of 15
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Re: sending emails deffered

The thing is greylisting is meant to be a tool for weeding out spambots from legitimate mail servers.  It's based on the principle that the majority of spambots give up after the first attempt, whereas mail servers will retry the connection as recommended in the RFC's.  So while a poor reputation may indicate that the IP address deserves closer inspection in the first place, once it's identified it's talking to a mail server, it shouldn't be rejecting the mail.

Incidentally, greylisting on IP alone is not ideal.  The greylisting RFC, suggests using a tuple of information.

Server IP
HELO/EHLO identity
mail from: address

And then once it's established it's talking to a mail server, it can whitelist the server temporarily, so it's not deferring every send from the same server.

Source https://tools.ietf.org/html/rfc6647

Tim

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