Host not reachable (Email not Receiving and Sending)

Hi, we are facing this issue for our 3 Email ID

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 Wed, 15 May 2024 09:11:08 -0700
from info@amcqatar.co [info@amcqatar.co]

----- The following addresses had fatal errors -----
[finance@amcqatar.co]

Message will be retried for 4 more day(s)

Reporting-MTA: dns; mx.zohomail.com
Arrival-Date: Wed, 15 May 2024 18:25:22 +0300

Original-Recipient: rfc822; finance@amcqatar.co
Final-Recipient: rfc822; finance@amcqatar.co
Status: 421
Action: failed
Last-Attempt-Date: 15 May 2024 16:11:08 GMT
Diagnostic-Code: Host not reachable.
Remote-MTA: dns; 34.193.26.244

Received:from mail.zoho.com by mx.zohomail.com
with SMTP id 1715786722115249.70078847015384; Wed, 15 May 2024 08:25:22 -0700 (PDT)
Message-ID:<18f7cdbab2c.eba4ca0339297.4888677325574706369@amcqatar.co>
Date:Wed, 15 May 2024 18:25:22 +0300
From:Info - AMC <info@amcqatar.co>
To:"finance" <finance@amcqatar.co>
Subject:Testing
Content-Type:multipart/alternative;
boundary="----=_Part_123349_1206968631.1715786722092"
User-Agent:Zoho Mail

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