Emails sent through Mailchannels not being delivered to Plusnet

[#1]

Hello,

One of my clients has two Plusnet members in their organisation. Emails do not reach them and the error from Plusnet's mail server is "552 Spam Message Rejected". The email is not spam though, and it can be delivered if sent from a different email account..

These emails are sent through cPanel based email accounts running Mailchannels, a service used to prevent spam being sent.

Delivery report:

Reporting-MTA: dns; relay.mailchannels.net
X-Postfix-Queue-ID: 556D1C1246
X-Postfix-Sender: rfc822; ####@##########.org.uk
Arrival-Date: Mon, 10 Jun 2024 12:05:15 +0000 (UTC)

Final-Recipient: rfc822; ###@######.plus.com
Original-Recipient: rfc822;###@######.plus.com
Action: failed
Status: 5.0.0
Remote-MTA: dns; mx.avasin.plus.net
Diagnostic-Code: smtp; 552 Spam Message Rejected

It is the same for both recipients at Plusnet.

Please can someone help me resolve this?

[#2]

You appear to be sending from a dmian address, does your domain have an SPF record which includes mailchannels?

https://support.mailchannels.com/hc/en-us/articles/200262610-Set-up-SPF-Records

[#3]

Thanks for reply.

cPanel account SPF:

v=spf1 +a +mx +ip4:78.110.163.50 include:_spf-uk09.webhostcluster.com ~all

The include:_spf-uk09.webhostcluster.com references Mailchannels:

v=spf1 +ip6:2a01:a500:3145:50::50 +include:relay.mailchannels.net -all

 I have amended the cPanel account SPF to include it directly, just in case this helps:

v=spf1 +a +mx +ip4:78.110.163.50 include:_spf-uk09.webhostcluster.com include:relay.mailchannels.net ~all

[#4]

In that case I suggest you contact Customer support on +44-330-1239-123 . There is now a procedure (even for non-plusnet customers) by which email spam rejections can be investigated. They ought to be able to contact 2nd line support who may request further information e.g message headers.

Please post back to indicate how the contact with CS was handled

[#5]

@bkno did you get a sensible response from Customer services ?

[#6]

I had a reply from customer service (via X):

"Plusnet doesn't block anything this may be down to SPF records and this is something the customer needs to change on their own. We do not block anything as the customer has the ability to block these things themselves."

Seems unlikely they "don't block anything" as most email systems will have a spam filter.

Waiting for my client to get an opportunity to test it further after I tweaked the SPF, and also so we have a bit more data/evidence of a pattern.

I'll try the customer support number then so it is raised properly.

[#7]

@bkno thanks for the update.

I had a reply from customer service (via X):

"Plusnet doesn't block anything this may be down to SPF records and this is something the customer needs to change on their own. We do not block anything as the customer has the ability to block these things themselves."

I can't say I'm entirely surprised at that response via X

Seems unlikely they "don't block anything" as most email systems will have a spam filter.

You're absolutely correct, they use the Cloudmark system for spam filtering.

Waiting for my client to get an opportunity to test it further after I tweaked the SPF, and also so we have a bit more data/evidence of a pattern.

I'll try the customer support number then so it is raised properly.

If you could do that please, and post back here with information as to the response you get.

This sort of problem has been discussed in the Superusers group and as a result, a procedure has been defined to enable Customer support to instigate investigation of  such. We (the Su's) would like to establish if the procedure is working and if not, to push back to get some traction on the issue.