Postfix Configure Client SMTP Authentication ( Smarthost Authentication )

To configure client SMTP authentication (also known as "smarthost authentication") in Postfix, you can use the sasl_password_maps and smtp_sasl_auth_enable parameters in the main.cf configuration file.

The sasl_password_maps parameter specifies a lookup table that contains the credentials for the smarthost. The table can be in the form of a text file, a database, or a program that generates the table on-the-fly.

The smtp_sasl_auth_enable parameter enables SASL authentication for the Postfix SMTP client.

To configure client SMTP authentication in Postfix, follow these steps:

1. Create a text file that contains the credentials for the smarthost. The file should contain one entry per line, with the format client_name username:password. For example:

smarthost.example.com user1:password1

2. Use the postmap utility to build a lookup database from the text file. For example:

# postmap /etc/postfix/sasl_passwd

This will create a database file named sasl_passwd.db.

3. Add the sasl_password_maps parameter to the main.cf configuration file and specify the path to the database file. For example:

sasl_password_maps = hash:/etc/postfix/sasl_passwd

4. Add the smtp_sasl_auth_enable parameter to the main.cf configuration file and set it to yes. This will enable SASL authentication for the Postfix SMTP client.

smtp_sasl_auth_enable = yes

5. Restart the Postfix service to apply the changes.

It's important to note that this is just one example of how to configure client SMTP authentication in Postfix. There are many other parameters and settings that you can configure