Everything goes smooth when i connect with Outlook to the server, but I can't sent anything. I can receive e-mails from anywhere but I can only send to user@mydomain. The error: The message could not be sent because one of the recipients was rejected by the server. The rejected e-mail address was 'firstname.lastname@example.org'. Subject 'test', Account: 'xxxxxxx.ro', Server: 'xxxxxxx.ro', Protocol: SMTP, Server Response: '554 <email@example.com>: Recipient address rejected: Relay access denied', Port: 25, Secure(SSL): No, Server Error: 554, Error Number: 0x800CCC79 I tryed SMTP without authentification and it does not connect to the server at all. I checked, I have the co-domain created, and in etc/postfix/local-host-names I have too the co-domain. What can I do?