Emails rejected as spam with 552 error

[#1]

I'm sending this from my mother's account, as she is having an issue with emailing one particular domain - that of her mother's care home. Several other people have reported a similar issue, and seem to have had it resolved.

Emails from this domain arrive fine, and a "new" email goes through okay, but if you reply (or forward) the email they get bounced:

Your message did not reach some or all of the intended recipients.

      Subject:    RE: Communication

      Sent: 03/08/2022 09:20

The following recipient(s) cannot be reached:

      'admin@DOMAIN.COM' on 03/08/2022 09:20

            552 J9c7ogBbOiXxBJ9c8o9zee 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.

Other messages here seem to indicate this is a Cloudmark problem, and to solve it we will need to send a copy of the message headers to someone to resolve it. If this is the case, please let me know who to send it to.

[#2]

Hi there,

If you can PM me a full copy of the bounceback along with the headers, I'll raise a NetOps task to take a look for you. 

[#3]

I'm trying to send a reply via PM, but get an "access denied" error when I go to the private messages section.

[#4]

@kmrobinson 

Try making 3 more posts here, then try again.

[#5]

@kmrobinson  Once you have made 3 posts you should be able to use PM

[#6]

Thanks, hopefully posting this will give me access!

[#7]

Thanks for this