Sendmail, 3rd Edition

Support SMTP AUTH

Support for the SMTP extension AUTH, as defined by RFC2554, was first included in sendmail beginning with V8.10. In this section we first show how to include AUTH support inside sendmail, then how to verify that it works, and finally, how to use it. The steps to take are:

• Download, compile, install, and configure the Cyrus SASL library.

• Build and install sendmail with SASL support included.

• Configure your client machines to use SASL.

Before we begin, however, let’s consider why you might want AUTH support, or why you might not need it.

SMTP AUTH is intended to prevent untrusted machines from using your mail-sending machines to send undesirable mail, such as spam. If yours is just a lone Linux box used to send and receive personal email, and you don’t travel, SMTP AUTH will probably not be of use to you. For SMTP AUTH to have value, yours must be a network that supports laptops or other portable machines that can be removed and installed without system administration oversight, and where those permanent machines all need to trust each other. The larger your site, the more likely it is that you will need to use SMTP AUTH as one more layer of email protection. A mail gateway machine that is a frontend for many PC and laptop machines is one situation where such trust is desirable, and we will use it as an example throughout this section.

Get and Install the SASL Library

As of this writing, the Cyrus SASL library is available from ftp://ftp.andrew.cmu.edu/pub/cyrus-mail ...