Qsmtpd was written by Rolf Eike Beer <qsmtp@opensource.sf-tec.de>. It is
licensed under GPL, version 2.

It includes some work from other peoples:

=============== TLS stuff =================
TLS stuff is taken from "netqmail-1.05-tls-20040419.patch", which has the
following credits:

Frederik Vermeulen <qmail-tls akrul inoa.net> 20040419
http://inoa.net/qmail-tls/

Copyright: GPL
           Links with OpenSSL
           Inspiration and code from examples in SSLeay (E. Young
           <eay@cryptsoft.com> and T. Hudson <tjh@cryptsoft.com>),
           stunnel (M. Trojnara <mtrojnar@ddc.daewoo.com.pl>),
           Postfix/TLS (L. Jaenicke <Lutz.Jaenicke@aet.tu-cottbus.de>),
           modssl (R. Engelschall <rse@engelschall.com>),
           openssl examples of E. Rescorla <ekr@rtfm.com>.

=============== AUTH stuff =================
The authentication part is taken from qmail-smtpd-auth-0.31, which has
this credits:

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>.

Beginning with version 0.30, the patch was completely rewritten to
use only djb's string functions by Eric M. Johnston <emj@postal.net>.