some emails are returning with this msg: Client host rejected: cannot find your hostname

some emails are returning with this msg: Client host rejected: cannot find your hostname

 
    
  
  1. Delivered-To: ---@---.com.br Received: from mail.zoho.com by mx.zohomail.com with SMTP id 1484740728810557.2206145808678; Wed, 18 Jan 2017 03:58:48 -0800 (PST) Date: Wed, 18 Jan 2017 03:58:48 -0800 From: mailer-daemon@mail.zoho.com To: ---@---.com.br Message-Id: <159b17197ca.11ad2ef9e-1253500143.-3521103138858408196@zohomail.com> Subject: Undelivered Mail Returned to Sender MIME-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_1379_1353811689.1484740728777" User-Agent: Zoho Mail X-Mailer: Zoho Mail X-ZohoMail: Z_66344739 SPT_1 Z_66344738 SPT_1 Si CHF_MF_NL SS_10 UW48 UB48 FMWL UW48 UB48 SGR3_1_2_0_27046_43 X-Zoho-Virus-Status: 2 ------=_Part_1379_1353811689.1484740728777 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable This message was created automatically by mail delivery software. A message that you sent could not be delivered to one or more of its recip= ients. This is a permanent error.=20 ---@terra.com.br, ERROR_CODE :554, ERROR_CODE :mail-cmgw03-mia.tpn.= terra.com cmsmtp Client host rejected: cannot find your hostname 74.201.84.= 163 Received:from iMac-de-Joao.local (191.---.120.48 [191.---.120.48]) by mx.z= ohomail.com =09with SMTPS id 1484740727640193.37217353636947; Wed, 18 Jan 2017 03:58:47= -0800 (PST) Message-ID:<1d3714a6-e7b0-ee8b-28e2-dd43f9edc6fe@fortunata.com.br> Date:Wed, 18 Jan 2017 09:58:46 -0200 From:Jo=C3=A3o - Fortunata <---@---.com.br> User-Agent:Mozilla/5.0 (Macintosh; Intel Mac OS X 10.12; rv:45.0) Gecko/20100101 Thunderbird/45.6.0 To:Ivania - Ideal <---@terra.com.br> Subject:2a via Content-Type:text/plain; charset=3Dutf-8; format=3Dflowed ------=_Part_1379_1353811689.1484740728777-- 
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do you know whats wrong ?