mx.bt.lon5.cpcloud.co.uk has blocked Google MX mail-pf1-f198.google.com (209.85.210.198)

[mw2870]

Sending an email from Google to BT Internet and the message was rejected with the following message:

Google tried to deliver your message, but it was rejected by the server for the recipient domain <a href="http://btinternet.com" target="_blank">btinternet.com</a> by <a href="http://mx.bt.lon5.cpcloud.co.uk" target="_blank">mx.bt.lon5.cpcloud.co.uk</a>. [65.20.0.49]. The error that the other server returned was: 421 Policy (1.2.6.1) Too much SPAM received from 209.85.210.198 on 2019/02/01 11:41:07 GMT, if you share a mail server consider moving to a dedicated mail server not sending SPAM. Guide for senders <a href="http://www.bt.com/postmaster" target="_blank">www.bt.com/postmaster</a>

Surely Google's MX's should be Whitelisted given the number of users who use Google's mail services?

[mw2870 · Accepted solution]

Seems like this is just some sort of cooldown.

Mail was first attempted to be delivered at 11:41. Rejected 4 times, then finally accepted @ 13:32.