Good afternoon, when sending messages such message sometimes appears.

INVALID_ADDRESS, ERROR_CODE :550, ERROR_CODE :relay not permitted 
Reporting-MTA: dns; mx.zoho.com 
Arrival-Date: Thu, 11 Jul 2019 17:56:49 +0300 
Original-Recipient: rfc822; 
Final-Recipient: rfc822; 
Status: 550 
Action: failed 
Last-Attempt-Date: 11 Jul 2019 14:56:59 GMT 
Diagnostic-Code:   INVALID_ADDRESS, ERROR_CODE :550, ERROR_CODE :relay not permitted 
Received:from (91.149.173.137 [91.149.173.137]) by mx.zohomail.com 
    with SMTPS id 1562857013627404.66395802160264; Thu, 11 Jul 2019 07:56:53 -0700 (PDT) 
Message-ID:<1bdff01d537f8$df3d95f0$9db8c1d0$@*******> 
Date:Thu, 11 Jul 2019 17:56:49 +0300 
From:******
To:******
Subject:RE: 
Content-Type:multipart/mixed; 
    boundary="----=_NextPart_000_1BE00_01D53812.048C2D80"