Legitimate Emails being rejected as spam

[#1]

I am looking for a contact within PlusNet that can help.

I manage tan email service for a large walking organisation within the UK.  Emails are broadcast to the members on a regular basis over a month.  Many of the members use Plusnet as their ISP.  Some of the emails being received by PlusNet are being rejected  as spam, when they are legitimate emails.  The delivery status being returned  is

"delivery-status": {
"tls": true,
"mx-host": "mx.avasin.plus.net",
"attempt-no": 1,
"description": "",
"session-seconds": 2.71600604057312,
"code": 552,
"message": "Spam Message Rejected ",
"certificate-verified": true
},

Is there anyone within plusnet that could assist in resolving this.  There are a large number of  member not receiving these important emails.

Kind Regards

Richard Handford

[#2]

Hi Richard,

A warm welcome to the forums.  It would greatly assist staff if you can provide...

1. Sample email subject lines
2. Date / time sent
3. Your SMTP server IP address / Domain
4. The 552 rejection signatures

This issue will require investigation by tech support staff, rather than first line support, so supplying the above information might get a quicker response for you.

@JW 

[#3]

Thank You for your reply I have sent you a pm.

Kind Regards

Richard Handford