Bounced email with ResponseCode 421 (Read timed out)

Bounced email with ResponseCode 421 (Read timed out)

Since last Friday I had issue where all my emails to client's particular domains (hosted in the same in-house mail server using mDaemon) with ResponseCode 421 (Read timed out). It was working well before Friday. I have asked them to check whether Zoho SMTP is on RBL. My computer is clean of virus and I sent nothing but regular email or doc/ppt attachment. This is very critical. What's wrong with Zoho? How to fix this?



Delivered-To: xxxx@rise.biz.id
Received: from mail.zoho.com by mx.zohomail.com
with SMTP id 1427115256332525.2534090055676; Mon, 23 Mar 2015 05:54:16 -0700 (PDT)
Date: Mon, 23 Mar 2015 05:54:16 -0700
From: mailer-daemon@mail.zoho.com
To: xxxx@rise.biz.id
Message-ID: < 14c46b2a9ca.11b5b5e5c833563991.1530183157563026884@zohomail.com>
Subject: Mail Delivery Status Notification (Delay)
MIME-Version: 1.0
Content-Type: multipart/mixed;
boundary="----=_Part_21296_130074775.1427115256266"
User-Agent: Zoho Mail
X-Mailer: Zoho Mail
X-ZohoMail: Si CHF_MF_NL SS_10 UW48 UB48 COSF2D FMWL UW48 UB48 SGR3_1_19035_50
X-Zoho-Virus-Status: 2


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, 23 Mar 2015 05:54:16 -0700 from xxxx@rise.biz.id [ xxxx@rise.biz.id]

----- The following addresses had fatal errors -----
[Status: Error, Address: < xxxxx@somedomain1.co.id>, ResponseCode 421, Read timed out, Status: Error, Address: < xxxxx@somedomain2.co.id>, ResponseCode 421, Read timed out]

Message will be retried for 4 more day(s)

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

Received:from RISE1 (202.77.109.xxx [202.77.109.xxx]) by mx.zohomail.com
with SMTPS id 1427111583823312.2081299879791; Mon, 23 Mar 2015 04:53:03 -0700 (PDT) Message-ID:<001701d0655f$ecedcb90$c6c962b0$@rise.biz.id>
Date:Mon, 23 Mar 2015 18:53:03 +0700
From:"sender name" < xxxx@rise.biz.id> To:"client name 1" < xxxxx@somedomain1.co.id>,
"client name 2" < xxxxx@somedomain2.co.id> Subject:test email Content-Type:multipart/alternative;
boundary="----=_NextPart_000_0018_01D0659A.994CA390"