qmail (sometimes incorrectly written "Qmail") is a mail transfer agent that runs on Unix. It was written by Daniel J. Bernstein as a more secure replacement for the popular Sendmail program. Only two minor bugs have been found in qmail since version 1.0, and there is an as yet unclaimed $500 prize for the first person to publish a verifiable security hole in the latest version of the software.
qmail encourages the use of several innovations in mail (some originated by Daniel J. Bernstein, others not), including maildir format mailboxes for storing messages ( mbox files are also supported, and encouragement to migrate is given along with a tool to convert mbox mailboxes to maildir mailboxes) and the QMTP and QMQP protocols.
qmail's major competitors are Exim and Postfix.
1 Copyright Status
qmail is unusual in that it does not include a lengthy software license. qmail is copyrighted by Bernstein, and distributed as freeware. Permission is granted to redistribute the unmodified source and binary packages, but not any modified versions of the software. Bernstein has a web page about software law in which he explains his belief that software users are always allowed to modify software for their own personal use, regardless of license agreements. Bernstein says "As long as you're not distributing the software, you have nothing to worry about."
He also says that "since it's not copyright infringement for you to apply a patchIn computing, a patch is a software update meant to fix problems with a computer program. This can range from fixing bugs to replacing graphics to improving the usability or performance of a previous version. The term probably originates from the Unix pat, it's also not copyright infringement for someone to give you a patch." Following this, modified versions of qmail such as netqmail and DebianDebian created by the Debian Project is a widely used distribution of free software developed through the collaboration of volunteers from around the world. Since its inception, the released system, Debian GNU/Linux, has been based on the Linux kernel wit's qmail-src package are legally distributed by packaging Bernstein's unmodified qmail sources with a diffIn computing, diff is a Unix utility that outputs the difference between two text files. The output of this program is also called a diff''. It is invoked from the command line with the name of two files: $ diff firstone. txt secondone. txt The first edit of the modifications, and sometimes including a script to automatically patchIn computing, a patch is a software update meant to fix problems with a computer program. This can range from fixing bugs to replacing graphics to improving the usability or performance of a previous version. The term probably originates from the Unix pat and compile qmail.
Because actual distribution of the modified source code is not allowed, qmail does not meet the OSIThe Open Source Initiative is an organization dedicated to promoting open source software. It was founded in February 1998 by Bruce Perens and Eric S. Background In 1997, Eric S. Raymond presented his revolutionary paper on software engineering, The Cathe's definition of "open source"The Open Source Definition is used by the Open Source Initiative to determine whether or not a software license can be considered open source. The definition was based on the Debian Free Software Guidelines, written and adapted primarily by Bruce Perens. or the FSF's definition of "free software". As a consequence, many Linux distributions may not or will not include qmail. Since other MTAs are commonly included in distributions, this may have negatively affected qmail's popularity. Nonetheless, fans of qmail point out that it is "free enough" for anyone to use, and the licensing issues haven't stopped a number of feature-enhancing patches from being published.
