What is is: [excerpt taken from README.auth from the patch]

This patch adds ESMTP AUTH authentication protocol support to
qmail-1.03.  It's originally based on Mrs. Brisby's smtp-auth patch
with many enhancements from Krzysztof Dabrowski <brush@elysium.pl>.

You can always get the newest version from:
http://members.elysium.pl/brush/qmail-smtpd-auth/

To use all of it's functionality you will also have to obtain and
install Krzysztof's cmd5checkpw utility available at:
http://members.elysium.pl/brush/cmd5checkpw/

If you need more information about SMTP-AUTH itself and the
client/server support and configuration, visit:
http://members.elysium.pl/brush/smtp-auth/

Neal Groothuis glued both ESMTP AUTH and TLS patches together and
then we have this port.

Author: Neal Groothuis <ngroot@imsa.edu>
WWW: http://www.qmail.org/