Email Bounce Back Issue

Hi Team i am currently having difficulties in sending emails to few of our clients. The email i sent is not reaching their end; it bounce back. can anyone asssist me on this issue and how to resolve it..

Find below is the email of one of the email that was sent to a client and bounce back.

Delivery has failed to these recipients or groups:

mailto:jospehine.Oa@telikom.com.pg
A problem occurred and this message couldn't be delivered. Check to be sure the email address is correct. If the problem continues, please contact your helpdesk.

Diagnostic information for administrators:

Generating server: cuda1.online.net.pg

mailto:jospehine.Oa@telikom.com.pg
Remote Server returned '< #5.4.4 X-Email-Security-Gateway; Host or domain name not found. Name service error for name=telikom.com.pg type=A: Host not found>'

Original message headers:

Return-Path: <mailto:it@sia.gov.pg>X-ASG-Debug-ID: 1600735452-141c8041382e63b0001-aanroaReceived: from mail.sia.gov.pg (mail.sia.gov.pg [203.83.19.164]) by cuda1.online.net.pg with ESMTP id PtTjd9kvS9Nj2KD0 (version=TLSv1 cipher=ECDHE-RSA-AES256-SHA bits=256 verify=NO) for <mailto:jospehine.Oa@telikom.com.pg>; Tue, 22 Sep 2020 10:44:13 +1000 (+10)X-Barracuda-Envelope-From: mailto:it@sia.gov.pgX-Barracuda-Effective-Source-IP: mail.sia.gov.pg[203.83.19.164]X-Barracuda-Apparent-Source-IP: 203.83.19.164X-Barracuda-OUTBOUND: YesReceived: from SIAEX01.sia.local (192.168.1.2) by SIAEX01.sia.local (192.168.1.2) with Microsoft SMTP Server (TLS) id 15.0.995.29; Tue, 22 Sep 2020 10:44:08 +1000Received: from SIAEX01.sia.local ([::1]) by SIAEX01.sia.local ([::1]) with mapi id 15.00.0995.028; Tue, 22 Sep 2020 10:44:08 +1000From: "Andrew AK. Kaiap" <mailto:it@sia.gov.pg>To: "mailto:jospehine.Oa@telikom.com.pg" <mailto:jospehine.Oa@telikom.com.pg>Subject: testThread-Topic: testX-ASG-Orig-Subj: testThread-Index: AdaQeXid5965f5swR2KBgHRFnCNR8w==Date: Tue, 22 Sep 2020 00:44:07 +0000Message-ID: <mailto:fe1f8ee97ba14371af843ba8232dda19@SIAEX01.sia.local>Accept-Language: en-AU, en-USContent-Language: en-USX-MS-Has-Attach: yesX-MS-TNEF-Correlator:x-bromium-msgid: 3e72f0b6-4d1d-42ba-814f-13268d8e0874x-originating-ip: [192.168.1.39]x-kse-antispam-interceptor-info: fallbackx-kse-antivirus-interceptor-info: fallbackContent-Type: multipart/related;    boundary="_004_fe1f8ee97ba14371af843ba8232dda19SIAEX01sialocal_";        type="multipart/alternative"MIME-Version: 1.0X-Barracuda-Connect: mail.sia.gov.pg[203.83.19.164]X-Barracuda-Start-Time: 1600735452X-Barracuda-Encrypted: ECDHE-RSA-AES256-SHAX-Barracuda-URL: https://10.99.18.36:443/cgi-mod/mark.cgiX-Barracuda-Orig-Rcpt: mailto:jospehine.Oa@telikom.com.pgX-Virus-Scanned: by bsmtpd at online.net.pgX-Barracuda-Scan-Msg-Size: 6330X-Barracuda-BRTS-Status: 1X-Barracuda-Spam-Score: 0.00X-Barracuda-Spam-Status: No, SCORE=0.00 using global scores of TAG_LEVEL=1000.0 QUARANTINE_LEVEL=3.0 KILL_LEVEL=4.0 tests=EXTRA_MPART_TYPE, HTML_MESSAGEX-Barracuda-Spam-Report: Code version 3.2, rules version 3.2.3.84786        Rule breakdown below        pts rule name              description        ---- ---------------------- --------------------------------------------------        0.00 EXTRA_MPART_TYPE       Header has extraneous Content-type:...type= entry        0.00 HTML_MESSAGE           BODY: HTML included in message