Request urgent help and suggestions on subjected error.

I am sending emails to my clients and getting this error every now and then with "just one client/domain"

When raised the issue to IT team of the client they replied "IP - 122.162.92.93 is blacklisted. Please refer to the screenshot attached"

The screenshot is referred here as well.

Thanks!

Saffi

saffii@rasantconsult.com

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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, 09 Dec 2015 04:43:49 -0800
from saffii@rasantconsult.com [saffii@rasantconsult.com]

----- The following addresses had fatal errors -----
[Status: Error, Address: <XXXXX.XXXX@XXXXX.com>, ResponseCode 421, 4.7.0 Temporarily Deferred]

Message will be retried for 4 more day(s)

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

Received:from Rasant (122.162.92.93 [122.162.92.93]) by mx.zohomail.com
    with SMTPS id 144966232563638.10393531870636; Wed, 9 Dec 2015 03:58:45 -0800 (PST)
Message-ID:<002301d13278$d7fb4cd0$87f1e670$@rasantconsult.com>
Date:Wed, 9 Dec 2015 17:27:25 +0530
From:"Saffi" <saffii@rasantconsult.com>
To:<XXXXX.XXXX@XXXXX.com>
Subject:XXXXXXXXXXXXXXXX 
Content-Type:multipart/mixed;
    boundary="----=_NextPart_000_0024_01D132A6.F1B69610"