exchange problem

we are using microsoft outlook 2016 as zoho exchange .to day i lost 5 e-mails .what can we do??i receive e-mail like that :

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, 21 Mar 2018 06:36:05 -0700
from john@reasonto.gr [ john@reasonto.gr]

----- The following addresses had fatal errors -----
[Status: DOMAIN_NOT_RESOLVED, Address: < info@teleactive.g>, DOMAIN_NOT_RESOLVED]

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 1521636658809124.46799419264528; Wed, 21 Mar 2018 05:50:58 -0700 (PDT)
Message-ID:<003401d3c113$406e34a0$c14a9de0$@reasonto.gr>
Date:Wed, 21 Mar 2018 14:50:54 +0200
From:John Gourtzelas < john@reasonto.gr>
User-Agent:Zoho Mail
To:< info@teleactive.g>
Cc:"'Michalis Charitopoulos / fiftyeggz'" < mike@fiftyeggz.gr>
Subject:RE: Reason to: νέοι τηλεφωνικοί Αριθμοί
Content-Type:multipart/related;
boundary="----=_NextPart_000_0035_01D3C124.0409C950"