552 Spam Message Rejected

[#1]

Can anybody tell my why an inbound message was bounced with the following message returned to the sender.
- - - - - - - - - - - - - -
A message that you sent could not be delivered to one or more of its recipients. This is a permanent error. The following address(es) failed:
  <snip>@<snip>.plus.com
    (generated from <snip>@<snip>.me.uk)
    SMTP error from remote mail server after end of data:
    host mx.avasin.plus.net [212.159.9.200]: 552 Spam Message Rejected
------ This is a copy of the message, including all the headers. ------
------ The body of the message is 246161 characters long; only the first
------ 16384 or so are included here.
<snip>

[#2]

Some details of the sender's domain & etc (snipped for privacy) might be helpful to someone more knowledgeable. Was the message sent using a webmail provider or using an email client?

[#3]

Quote from: Anotherone

Some details of the sender's domain & etc (snipped for privacy) might be helpful to someone more knowledgeable. Was the message sent using a webmail provider or using an email client?

I appreciate your reply and do have available the full headers from the bounced message which includes the domain name etc.  I can make everything available off line to a member of PlusNet staff and disappointed not to have received a response.  As far as I can tell the message was sent via an email client; Microsoft Outlook or Exchange Server.

[#4]

Hopefully Bob will respond, he's the man for this one 

[#5]

In the old days you could raise a "TICKET" and I always received a satisfactory reply within a reasoanble time.  PlusNet have "improved" things and as far as I can see tickets are a thing of the past.  Bob, are you there?  Come in please, my question has not gone away and I see others are experiencing a similar problem.  I have the full message headers for the bounced email.
dick:quote

[#6]

Drop me a PM and I'll try and take a look tomorrow.

[#7]

Thanks Bob, PM sent, look forward to your reply.

[#8]

Many thanks Bob, questions answered.
For the benefit of other members of this forum the inbound message for me was bounced by a PlusNet server, having fallen foul of Cloudmark (follow the link below for more information).  OK, some might say this is censorship but Cloudmark claims "greater than 99% accuracy and near zero false positives".  I am prepared to accept the occasional "false positive" in order to stop the flood of junk I am sure one would otherwise receive.  I have also "white listed" the sender's domain name so hopefully it won't happen again, at least for this particular sender.

Quote from: Bob

Hi, The email was bounced by our inbound delivery servers - mx.avasin.plus.net.  Most probably because the content of the email fell foul of Cloudmark Authority. Best regards, Bob.

[#9]

me too...
very first thing this morning I had a series of 7 emails not sent (to multiple BCCs)
example error message
"      'username@username.plus.com' on 03/12/2015 19:52
           552 p7rN1r0063rrg6n017rhY5 message rejected due to spam or virus. If you believe this is in error please login to your portal or contact your ISP support team."
This one was for the message sent back to myself to check send has worked
I do believe this to be in error - please fix it
dick:green Email address edited for the reason Bob gives below.

[#10]

Can you try sending the message using Webmail? Is should fail with the same error and end up in your Drafts folder where I can take a look at it (assuming you don't mind of course). As an aside, you might want to modify your post to remove your email address as it's likely to get harvested by spammers.