Another Error 552 when sending emails post

[#1]

Hi

I have a plusnet account, and use Outlook 2019 for my email which is sent using either gmail or plusnet email addresses.

I have been experiencing problems when sending some emails using my plusnet email address.
These mails are turning up in gmail inbox saying:

Mail Delivery Subsy.(mailer-daemon@googlemail.com)
Delivery Status Notification (Failure)

"Message not delivered"
There was a problem delivering your message to ****@******.plus.com.
See the technical details below.

552 Spam Message Rejected

I am able to forward these failure messages to a yahoo account, and then back to plusnet without problem, but I am unable to find a solution to cure the annoying problem of these messages not being delivered in the first place.

Also, I am unable to see any email addresses or subject on the failed messages, so I don't know who the rejected email addressee was/is

Any help will be greatly appreciated.

kind regards

gipper

[#2]

Hi @gipper 

A warm welcome to the forums.

There has been a spate of issues with emails sent from Gmail to Plusnet mailboxes with content, which when sent from other email providers, is not an issue.  Such seems to be re-enforced by your report that if these emails are sent from your Yahoo account, they do not fail.  There seems to be something about Gmail's formatting which is potentially causing a false positive on the SPAM services.

I recently examined an issue where there were 3 URLs in the email; sending an email from Gmail with each URL separately caused no issue; sending an email with one of the URLs with either of the other two gave rise to the 552 error.  Send the same URLs in any combination from an email provider other than Gmail and no issues were encountered.

Does the 552 error message provide a 'signature' code?

Are there any URLs in the email message which is being rejected?

[#3]

Hi Townman

Thanks for the welcome and for the reply. 

I'm not sure where I would find a signature code, but if you can advise I will certainly look.

Regarding query 2 - I cannot be sure if url's were included as I cannot even identify which email had failed, nor which addressee, or any other info, as all I am aware of is the actual failure message which turns up in gmail.

Is this bit the signature code?

"---------- Forwarded message ---------
From: Mail Delivery Subsystem <mailer-daemon@googlemail.com>
Date: Fri, 5 Jun 2020 at 09:19
Subject: Delivery Status Notification (Failure)
To: <nwwatterson+caf_=neilw=wattene.plus.com@gmail.com>  "

PS This failure of emails not being delivered has been going on for over a year. It's just been that with Covid I thought I would try and resolve the issue .

Cheers

gipper