Email undelivered Status 421

Email undelivered Status 421

For the most part my emails are working correctly, but one particular email every time I reply to them I get the abler status error code and the emails won’t be delivered. Any ideas how I can resolve this as soon as possible? I replied to it yesterday with no problems, this has only started today. 

This message was created automatically by mail delivery system. 

THIS IS A WARNING MESSAGE ONLY. 

YOU DO NOT NEED TO RESEND YOUR MESSAGE. 

The original message was received at Tue, 26 Oct 2021 23:25:55 +0200 
from alex.cameron@apautostyling.co.uk[alex.cameron@apautostyling.co.uk]  

----- The following addresses had fatal errors -----  
[recovery_operations+id26727230@shopify.zendesk.com] 

Message will be retried for 4 more day(s) 


Reporting-MTA: dns; mx.zohomail.eu 
Arrival-Date: Tue, 26 Oct 2021 21:40:28 +0100 

Original-Recipient: rfc822; recovery_operations+id26727230@shopify.zendesk.com 
Final-Recipient: rfc822; recovery_operations+id26727230@shopify.zendesk.com 
Status: 421 
Action: failed 
Last-Attempt-Date: 26 Oct 2021 21:25:55 GMT 
Diagnostic-Code: Host not reachable. 


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Message-ID:<17cbe55396c.dadc096c94022.7343775527621967437@apautostyling.co.uk> 
Date:Tue, 26 Oct 2021 21:40:28 +0100 
From:Alexron Came <alex.cameron@apautostyling.co.uk> 
To:"Recovery_operations Id26727230" 
<recovery_operations+id26727230@shopify.zendesk.com> 
Subject:Re: Shopify Capital and Shopify Payments Follow Up 
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