Setup Relay Host Port and SMTP Authentication Client in Postfix

This setup will help you to route all outgoing email through your ISP SMTP server using different port number and that SMTP server requires you to authenticate before relaying. For this scenario, the ISP SMTP server is Exim.
1. Edit this file /etc/postfix/ and add relayhost to point to your ISP SMTP server with port number as below: –
relayhost =
2. Add the next parameter to allow Postfix to authenticate before relaying outgoing email as below: –
smtp_sasl_auth_enable = yes Read More