Add the following to /etc/postfix/main.cf relayhost = smtpservices.studioemma.com:25 smtp_sasl_auth_enable = yes smtp_sasl_password_maps = hash:/etc/postfix/smarthost.conf smtp_sasl_mechanism_filter = CRAM-MD5,PLAIN,LOGIN smtp_saslsecurity_options = noanonymous Create file: /etc/postfix/smarthost.conf with content: smtprelay.host.be username:geheimpaswoord Execute: #postmap /etc/postfix/smarthost.conf Reload postfix service: service postfix reload Send a test email via: #mail -s “Test” you@mail.org this is a test body .