Error 550 Please turn on SMTP Auth

Error 550 Please turn on SMTP Auth

Hello,
currently some emails are randomly bouncing, and it doesn't make sense, this is the situation:
CBOS.cl is using Zoho (the MX records are setup correctly)
NORCHAM.cl is using Gmail (the MX records are setup correctly).

There are many emails @norcham.cl and @cbos.cl, however sometimes when one of the users try sending a mail from norcham.cl (google's mail), I get the following error:

From:  <mailer-daemon@mail.zoho.com>
Date: Tue, Jun 30, 2015 at 12:27 PM
Subject: Undelivered Mail Returned to Sender
To: account1@norcham.cl


This message was created automatically by mail delivery software.
 A message that you sent could not be delivered to one or more of its recipients. This is a permanent error.

account2@norcham.cl  Invalid Address, ERROR_CODE :550, ERROR_CODE :Please turn on SMTP Authentication in your mail client.
                         sender163-mail.zoho.com  [74.201.84.163]:25948 is not permitted to relay
                        through this server without authentication.
account3@norcham.cl  Invalid Address, ERROR_CODE :550, ERROR_CODE :Please turn on SMTP Authentication in your mail client.
                         sender163-mail.zoho.com  [74.201.84.163]:25948 is not permitted to relay
                        through this server without authentication.


 Received:from  mail-qg0-f43.google.com  ( mail-qg0-f43.google.com  [209.85.192.43]) by  mx.zohomail.com
        with SMTPS id 1435678049796569.552258052481; Tue, 30 Jun 2015 08:27:29 -0700 (PDT)
 Message-ID:< CAC+HkpFfAm-GE1JF5PW14SBXzPbpoLCC2sS8-ROtPJqHJj12_Q@mail.gmail.com >
 Date:Tue, 30 Jun 2015 12:27:27 -0300
 From:User1 < account1@norcham.cl >
 To:User4 < user4@gmail.com >
 Cc:User2 < user2@norcham.cl >, User3 < user3@norcham.cl >
 Subject:Re: cnc
 Content-Type:multipart/ alternative; boundary= 001a114705920db2950519bdd8eb

*This happened using Gmail (Not Outlook, or any other clients)