Plusnet SMTP server incorrectly rejecting outgoing email as spam

[#1]

I'm trying to send an email containing the text www.freeagentcrm.com

Any email containing that text, whether it is formatted as a link or is simply plain text, is rejected by Plusnet's SMTP server as follows:

SMTP Response: 552 rOmheUx0XT6RfrOmieyYB6 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.

I've tried sending to different recipients (myself included), all with the same result.

I've tried stripping out all the text in the email leaving only www.freeagentcrm.com and the rejection still occurs.

If I change the text to www.freeagent.com the email is not rejected.

Note that www.freeagentcrm.com is a valid (non-spam, non-phishing) business site (as is www.freeagent.com)

Why is this rejection happening please?

Plusnet can you fix it asap please, so I can send my legitimate email.

Thanks

[#2]

In wrong thread; use the one dedicated to E Mail.

[#3]

OK.  Thanks.

Re-posted in Email section

[#4]

Moderator's note:

Thread locked in favour of https://community.plus.net/t5/Email/Plusnet-SMTP-server-incorrectly-rejecting-outgoing-email-as-spam...