Email Rejected

[#1]

One of my addressees reported a problem to me today.  He received this message from Plusnet(?) :-

There was a problem delivering your message to "my email address". See the technical details below.

The response from the remote server was:

552 Spam Message Rejected

Could anyone explain what has happened and why.  VMTs

Boz

[#2]

For some reason the spam protection service has profiled that email as being potentially dangerous. There are a multitude of causes for reaching that conclusion…

The email contains suspicious content or links.

The sending domain or server has a bad reputation for sending junk email.

The anti-spam measures - SPF / DKIM / DMARC - failed validation.

Was the email sent direct to your @account.plus.com email address or via a third party email service?

Your correspondent should contact Plusnet support to request a spam rejection investigation.

[#3]

This has happened three times in the last few weeks to people sending to us - including twice to regular senders.  Has PlusNet changed their spam filtering algorithms recently?  If so, can they please change them back again!

[#4]

They have not explicitly change them. The spam service is provided by cloud mark which learns from dynamic user feedback what is considered to be spam. Thereby change is implicit from user experience.

[#5]

Hi guys

Thank you for your replies.

The “delivery failure notification” to my contact came from mailer-daemon@googlemail.com.  As the secretary of a club, he usually sends the same message to dozens of people.  So, it's unlikely that it contains “suspicious content or links”; or, indeed, that the domain he uses would be in the habit of sending junk mail.

It looks as if the email was sent direct to my Plusnet email address, although the “local part” of my contact’s email address does look a bit strange (i.e. not personalised).

There must surely be something significant about the number used in the notification.  Would there be a table of error messages somewhere that gives a clue as to what’s gone wrong?

Boz

[#6]

As the secretary of a club, he usually sends the same message to dozens of people. 

Ah! if he sends out the message with all the recipients as BCC , to hide everyones email address from the other recipients, and does not have a valid email address in the TO field (as is typical) , then from experience this will seriously increase the spam score of the emails.

[#7]

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@Boz wrote:

... or, indeed, that the domain he uses would be in the habit of sending junk mail.

There must surely be something significant about the number used in the notification.  Would there be a table of error messages somewhere that gives a clue as to what’s gone wrong?

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The domain he is using is @googlemail.com which is a notorious source of junk email.  If this is a club, its reputation would be enhanced significantly if it had a proper domain name / email address.

Yes, there is something significant about the number used in the notification - it indicates that the sending service encountered a permanent error and will not try again.  See 552 SMTP Error Code | SMTP Field Manual

What is not helpful is that the specific error has not been reported in the Googlemail non-delivery report - for example 552 5.7.1 virus [name] detected.

If one wanted something useful in the Googlemail non-delivery report, then the SPAM signature reference (returned by Plusnet in the rejection) would give a useful clue as to why the email is being profiled as suspect.

@MisterW 's observation is a common cause of bulk email's communications being considered to be likely to be spam.  

[#8]

@Townman Thank you so much for providing the link.  As you say it does require more specific information about the 552 error code.

@MisterW Your comments have prompted me to look more closely at the contact's email header.  And the first thing to notice is that the FROM and TO addresses are identical. My email address appears in the BCC field, which you've highlighted as a potential problem.  Thanks once again for your help.

Boz