Postfix: Configure SASL Authentication for Remote SMTP

Postfix SASL Authentication is one of the most popular methods for remote SMTP authentication. It’s a secure, reliable, and highly configurable way of sending and receiving emails. Essentially, the Postfix SASL Authentication consists of an authentication server and a client. The client is a mail program that sends the message, and the authentication server validates the credentials of the user. Once authentication is successful, the message is sent and authenticated at the receiving server.

The following step will configure the Postfix server to relay emails from a remote SMTP server with authentication.

1. First of all, configure the custom relayhost parameter. This will configure postfix to relay emails via the remote SMTP servers.

   sudo postconf -e "relayhost = smtp.gmail.com:587" 
   

   You can also configure the Postfix server for d relaying emails based on the sender address.

2. create an SMTP host and authentication mapping file:

   sudo nano /etc/postfix/smtp_sasl_password 
   

   Add your remote SMTP host and credentials one per line. See the below example:

   smtp.gmail.com           [email protected]:your_email_password
   

   Save the file and close it.

3. Next use the postmap command to update the Postfix lookup table for the above-created configuration file.

   sudo postmap /etc/postfix/smtp_sasl_password  
   

4. Update the Postfix main configuration file with the following commands:

   sudo postconf -e "smtp_sasl_auth_enable = yes"
   sudo postconf -e "smtp_sasl_password_maps = hash:/etc/postfix/smtp_sasl_password"
   sudo postconf -e "smtp_sasl_security_options ="
   

5. Finally, restart the Postfix service

   sudo systemctl restart postfix
   

6. All done. You can verify the changes by sending an email via the configured remote SMTP servers.

Postfix SASL Authentication provides a secure way to transfer emails, and it’s easy to set up. It also allows you to customize the authentication process, so if you want to use things like two-factor authentication or IP whitelisting, you can. Overall, Postfix SASL Authentication is a great option for anyone who needs a secure and reliable way to transfer emails. It’s a must-have for anyone who takes security seriously!