Cannot send to iCloud mailboxes due to blocked IP 185.20.211.225

p******@icloud.com, ERROR_CODE :550, ERROR_CODE :5.7.0 Blocked - see https://support.proofpoint.com/dnsbl-lookup.cgi?ip=185.20.211.225

Reporting-MTA: dns; mx.zohomail.eu
Arrival-Date: Sat, 4 Apr 2020 17:59:16 +0100
Original-Recipient: rfc822; p******@icloud.com
Final-Recipient: rfc822; p******@icloud.com
Status: 550
Action: failed
Last-Attempt-Date: 4 Apr 2020 16:59:21 GMT
Diagnostic-Code: p******@icloud.com, ERROR_CODE :550, ERROR_CODE :5.7.0 Blocked - see https://support.proofpoint.com/dnsbl-lookup.cgi?ip=185.20.211.225

Message-ID:<9B6AF535-8055-486B-8D8A-17671434EC63@****.co.uk>