EMail not reaching the recepient

EMail not reaching the recepient

Reporting-MTA: dns; mx.zohomail.com
Arrival-Date: Fri, 17 Nov 2023 19:14:41 +0400

Original-Recipient: rfc822; sales@redknox.ae
Final-Recipient: rfc822; sales@redknox.ae
Status: 421
Action: failed
Last-Attempt-Date: 17 Nov 2023 16:00:38 GMT
Diagnostic-Code: Host not reachable.