I receive this message each time i try to send an email.
Recipient address are good...but your mail system refuse to send.

This message was not with one contact, its persistant to all my contacts i've try to send an email.

I can receive mail without problem, but i can send.

This is the error message (name and email was changed for confidentiality)

user@domain.com  INVALID_ADDRESS, ERROR_CODE :554, ERROR_CODE :5.7.1 < user@domain.com >: Relay access denied 



Received:from mail.zoho.com by mx.zohomail.com 
    with SMTP id 1508245197957914.4786079446293; Tue, 17 Oct 2017 05:59:57 -0700 (PDT) 
Message-ID:<15f2a6b547@entreprise.com > 
Date:Tue, 17 Oct 2017 08:59:57 -0400 
From:Name Lastname <name.lastname@mydomain.com > 
User-Agent:Zoho Mail 
To:"Recipient name" < user@domain.com > 
Subject:test 4 
Content-Type:multipart/alternative; 
    boundary="----=_Part_110922_1511279013.1508245197955"