I have been continually receiving undelivered mail error messages after sending emails to valid addresses. Pasted below is the error message that I received. Any assistance on the root cause of this issue would be appreciated. Thank you.
"This is the mail system at host ns9.domainemailserver.com.
I'm sorry to have to inform you that your message could not
be delivered to one or more recipients. It's attached below.
For further assistance, please send mail to postmaster.
If you do so, please include this problem report. You can
delete your own text from the attached returned message.
The mail system
<e.martin-correa@afdb.org>: host
za-smtp-inbound-2.mimecast.co.za[41.74.197.210] said: 550 csi.mimecast.org
Poor Reputation Sender. -
https://community.mimecast.com/docs/DOC-1369#550 [YzlqdVrTPxCm77FGKLpF_Q.za34] (in reply to RCPT TO command)
Reporting-MTA: dns; ns9.domainemailserver.com
X-Postfix-Queue-ID: 7605A9000C1
X-Postfix-Sender: rfc822; andre.hessini@pjudbenin.org
Arrival-Date: Thu, 18 Jun 2020 23:45:08 +0200 (CEST)
Final-Recipient: rfc822; e.martin-correa@afdb.org
Original-Recipient: rfc822;e.martin-correa@afdb.org
Action: failed
Status: 5.0.0
Remote-MTA: dns; za-smtp-inbound-2.mimecast.co.za
Diagnostic-Code: smtp; 550 csi.mimecast.org Poor Reputation Sender. -
https://community.mimecast.com/docs/DOC-1369#550 [YzlqdVrTPxCm77FGKLpF_Q.za34]
Return-Path: <andre.hessini@pjudbenin.org>
Received: from localhost (localhost [127.0.0.1])
by ns9.domainemailserver.com (Postfix) with ESMTP id 7605A9000C1
for <e.martin-correa@afdb.org>; Thu, 18 Jun 2020 23:45:08 +0200 (CEST)
X-Virus-Scanned: Debian amavisd-new at ns9.domainemailserver.com
Received: from ns9.domainemailserver.com ([195.154.33.47])
by localhost (ns9.domainemailserver.com [127.0.0.1]) (amavisd-new, port 10024)
with ESMTP id uSMTyswDLg2U for <e.martin-correa@afdb.org>;
Thu, 18 Jun 2020 23:44:56 +0200 (CEST)
Received: from pjudbenin.org (localhost [127.0.0.1])
by ns9.domainemailserver.com (Postfix) with ESMTP id ADA189000C0
for <e.martin-correa@afdb.org>; Thu, 18 Jun 2020 23:44:55 +0200 (CEST)
MIME-Version: 1.0
Content-Type: multipart/mixed;
boundary="=_df9722e1c262f86b3f19021ba3a8e47e"
Date: Thu, 18 Jun 2020 16:44:55 -0500
From: andre.hessini@pjudbenin.org
To: e.martin-correa@afdb.org
Subject: Fwd: Demande de Financement de PJUD
In-Reply-To: <3c17f758bd6d91989ee111c9d8f66333@pjudbenin.org>
References: <079d588f18f5954e4b4c913b85402da1@pjudbenin.org>
<3c17f758bd6d91989ee111c9d8f66333@pjudbenin.org>
Message-ID: <8cecab6f9db1b2caf80ab4446776f9b8@pjudbenin.org>
X-Sender: andre.hessini@pjudbenin.org
User-Agent: Roundcube Webmail/1.3.8"