Let’s look into the details of Postfix with SASL authentication. At Bobcares, with our Server Management Services, we can handle your server-related issues.

Postfix with SASL authentication

SMTP servers must determine whether an SMTP client is permitted to send mail to remote destinations or just to those that the server is in charge of. SMTP servers often accept emails from distant recipients when the client’s IP address is on the “same network” as the server’s IP address.

A separate method is required for SMTP clients outside the network of the SMTP server to obtain “same network” rights. To meet this need, Postfix uses the SASL method. With this approach, both a remote SMTP client and the Postfix SMTP server may authenticate to a remote SMTP server. A server can provide “same network” access to a client once it has been successfully authenticated.

SASL is not implemented by Postfix. A few SASL-related setup files will be Postfix-specific, while others will be specific to the SASL implementation that Postfix will use.

Setup of Postfix with SASL authentication

The main two steps of the process are as follows:

1. Setting up authentication backends that compare the remote SMTP client’s authentication data against the system password file or another database, depending on the SASL, and configuring the SASL implementation to offer a list of mechanisms that are appropriate for SASL authentication.

2. Enabling SASL authentication, allowing clients permission to relay mail, or restricting the envelope sender addresses that clients are allowed to use.

A working SASL is necessary for the server’s authentication to be successful. Therefore, setting up SASL should always come first.

Setup of SASL authentication

We can find the following code to find out how SASL implementations are compiled into Postfix. Right now, the Dovecot and Cyrus implementations are supported by the server.

% postconf -a (SASL support in the SMTP server) % postconf -A (SASL support in the SMTP+LMTP client)

Postfix – Dovecot Implementation

Dovecot is a POP/IMAP server with a unique setup for POP/IMAP client authentication. Parts of this setup are reused by the Postfix SMTP server when it employs Dovecot SASL. Communication between the Postfix SMTP server and Dovecot SASL takes place over a UNIX-domain socket or a TCP socket. We will be using a UNIX-domain socket for improved privacy.

The Postfix queue is presumed to be located under /var/spool/postfix/ in the following code for Dovecot version 2.

Line 4 puts the Dovecot SASL socket in /var/spool/postfix/private/auth, lines 5-8 restrict read+write permissions to user and group postfix only, and also line 14 offers mechanisms for the Postfix SMTP server.

[Looking for a solution to another query? We are just a click away.]

Conclusion

The article provides a detailed explanation of Postfix with SASL authentication setup. The method used in this article is the Dovecot SASL Implementation.