Mail Not Delivered

Mail Not Delivered

Hi Team,

When I am trying to send email to recipients through Zoho help desk, But it doesn't deliver and it returns the below error message. 


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 Mon, 18 Sep 2017 06:31:21 -0700 
from  support@optisolbusiness.zohosupport.com [ support@optisolbusiness.zohosupport.com

----- The following addresses had fatal errors ----- 
[Status: Error, Address: < anitha.b@optisolbusiness.com>, ResponseCode 421, Host not reachable., Status: Error, Address: < jai@optisolbusiness.com>, ResponseCode 421, Host not reachable., Status: Error, Address: < balachandran.s@optisolbusiness.com>, ResponseCode 421, Host not reachable.] 

Message will be retried for 4 more day(s) 

----- Transcript of session follows ----- 

Received:from mail.zoho.com by mx.zohomail.com 
    with SMTP id 150573872445749.35215214047628; Mon, 18 Sep 2017 05:45:24 -0700 (PDT) 
Message-ID:<f14564b31679a112aab53dd1094e5dba91e21925ef6ee0bf6f31 42116ba97f52_2ma8u_15e95058fe8@zohodesk.com
Date:Mon, 18 Sep 2017 05:45:24 -0700 
From:Zoho Support < support@optisolbusiness.zohosupport.com
User-Agent:Zoho Mail 
To:< jai@optisolbusiness.com
Cc:" balachandran.s@optisolbusiness.com" < balachandran.s@optisolbusiness.com>, 
    "anithaletchumi b" < anitha.b@optisolbusiness.com>, 
     < support@optisolbusiness.zohosupport.com
Subject:Re:[## 355 ##] Install MS-Excel-High 
Content-Type:multipart/alternative; 
    boundary="----=_Part_74131_349788973.1505738724455"