virginmedia SMC Policy Violation bounce error

[CWildeRE]

Hi,

We're an ESP sending emails on behalf of cleints who are receiving the following bounce error from virgin media domains (blueyonder, ntlworld, virginmedia) across multiple different domains and IPs:

SMTP service unavailable: "421 4.2.0 MXIN618 Temporary SMC Policy Violation detected, retry later ;id=KdKFlqEMxa7TsKdKFlL2Ap;sid=KdKFlqEMxa7Ts;mta=mx12.tb;dt=2021-03-12T09:39:16+01:00;ipsrc=xx.xx.xx.xx;" received from mx.tb.ukmail.iss.as9143.net (212.54.56.11) while connected from SENDINGDOMAIN.co.uk (xx.xx.xx.xx) to mx.tb.ukmail.iss.as9143.net (212.54.56.11)

 We have tried "sending later", as suggested in the error but no emails are being allowed through. Would someone please be able to help me with the cause of this error, and how we may resolve it moving forwards? I can't find any information on it online nor action I can take for it to be removed.

If there is elsewhere better to post this question, please let me know and I'll be happy to move it.

Many thanks,

Chris

[CWildeRE]

I've managed to send a message to you now, it will be a fresh message from the one you previously sent to me.

[Hayley_S]

Hello!

Thank you for sending me this 🙂

I have someone looking into this for you but It will be Monday now when I get a update.

I will make sure I chase this up when I come in Monday and get back to you ASAP.

I hope this is okay for now 🙂

Thanks,

[CWildeRE]

Perfect, thanks Hayley!

[ravenstar68]

@HowardML 

It's not Graylisting.

Graylisting is when a client temporarily pushes back a mail transaction.  Normally it will monitor a tuple (multiple bits of information) such as IP address, Mail From: , Rcpt to:  and will only accept a retry after a specific period of time has passed.

This would normally happen before the DATA portion of the email send AFAIK.

I've no idea what the abbreviation SMC means in SMC policy violation.  Although the fact that we see an error code of 6xx would suggest that it's related to the content of the email itself - (The client sends a DATA command and then after the client sends a go ahead message, sends the email itself).

Tim

[HowardML]

@ravenstar68 

I was repeating what I found in the "Dutch" example I linked to. There the "victim" of the error said that Ziggo had told him it was greylisting. I am intrigued to know what it is then and happy to be corrected. We really need to have these error codes shared with the VIPs, as we do for the equivalent SMTP error codes. No one has ever seen this before. 

[ravenstar68]

I use graylisting on my server so I know the difference between graylisting and whatever this is

Here's postgrey in action on my server

Mar 12 12:04:26 box postgrey[1184]: action=greylist, reason=new, client_name=o8.pigeon.quora.com, client_address=52.20.90.87/32, sender=noreply@quora.com, recipient=*********@timothydutton.co.uk
Mar 12 12:04:26 box postfix/smtpd[28456]: NOQUEUE: reject: RCPT from o8.pigeon.quora.com[52.20.90.87]: 450 4.2.0 <*********@timothydutton.co.uk>: Recipient address rejected: Greylisted, see http://postgrey.schweikert.ch/help/timothydutton.co.uk.html; from=<noreply@quora.com> to=<*********@timothydutton.co.uk> proto=ESMTP helo=<o8.pigeon.quora.com>
Mar 12 12:07:45 box postgrey[1184]: action=pass, reason=triplet found, delay=355, client_name=o19.pigeon.quora.com, client_address=52.202.67.230/32, sender=noreply@quora.com, recipient=**********@timothydutton.co.uk

Tim

The fact is a lot more servers are now using 4xx error codes when in the past they would have used 5xx error codes to reject a problem mail outright.  The server will only accept the mail once the cause of the rejection has been rectified.

[HowardML]

@ravenstar68 

Such an interesting discussion.  Heaven only knows what we are seeing then - and I take your point (as I always do) that the conclusion I have drawn, from the evidence I have seen, may be mistaken.  After all is was a 4xx server error. We must have transparency on this when we get the conclusion. 

I've been having discussions about the need for transparency with @Kev_B in cases like this. This is a case where VM customers are only represented indirectly by the OP.  The OP is not a customer. So I'm directing this thread towards his in-tray so he can be aware.

@Hayley_S - to note where this discussion may be going. Lovely introduction to your new role! 

[HowardML]

@Hayley_S 

@CWildeRE 

@Kev_B 

I'm not going to let this one out of my sight!  Any news on what has been causing this error, and the reasons, for this particular ESP sending to VM mail domains, please?

[Hayley_S]

Hello @HowardML,

Unfortunately no news as of yet, the IT ticket is still being looked into.

I will post an update once I have received further information regarding this.

Thanks for your patience whilst our team investigates. 

Thanks, 

[CWildeRE]

To give an update here, it seems that over the past 2 weeks the issue has been resolved and emails are no longer being blocked, however I've not had any response as to what the issue/resolution was in the end.