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Sendmail is a general purpose
internetwork Internetworking is the practice of interconnecting multiple computer networks, such that any pair of hosts in the connected networks can exchange messages irrespective of their hardware-level networking technology. The resulting system of interc ...
email Electronic mail (email or e-mail) is a method of exchanging messages ("mail") between people using electronic devices. Email was thus conceived as the electronic ( digital) version of, or counterpart to, mail, at a time when "mail" mean ...
routing facility that supports many kinds of mail-transfer and delivery methods, including the
Simple Mail Transfer Protocol The Simple Mail Transfer Protocol (SMTP) is an Internet standard communication protocol for electronic mail transmission. Mail servers and other message transfer agents use SMTP to send and receive mail messages. User-level email clients typica ...
(SMTP) used for email transport over the
Internet The Internet (or internet) is the global system of interconnected computer networks that uses the Internet protocol suite (TCP/IP) to communicate between networks and devices. It is a '' network of networks'' that consists of private, pub ...
. A descendant of the ''
delivermail The ancestor of sendmail, delivermail, also by Eric Allman, is a mail transport agent that used the FTP protocol on the early ARPANET to transmit e-mail to the recipient. Due to deficiencies in using FTP to send e-mail, a new protocol was created ...
'' program written by
Eric Allman Eric Paul Allman (born September 2, 1955) is an American computer programmer who developed sendmail and its precursor delivermail in the late 1970s and early 1980s at UC Berkeley. In 1998, Allman and Greg Olson co-founded the company Sendmail, I ...
, Sendmail is a well-known project of the
free and open source software Free and open-source software (FOSS) is a term used to refer to groups of software consisting of both free software and open-source software where anyone is freely licensed to use, copy, study, and change the software in any way, and the source ...
and
Unix Unix (; trademarked as UNIX) is a family of multitasking, multiuser computer operating systems that derive from the original AT&T Unix, whose development started in 1969 at the Bell Labs research center by Ken Thompson, Dennis Ritchie, an ...
communities. It has spread both as
free software Free software or libre software is computer software distributed under terms that allow users to run the software for any purpose as well as to study, change, and distribute it and any adapted versions. Free software is a matter of liberty, no ...
and
proprietary software Proprietary software is software that is deemed within the free and open-source software to be non-free because its creator, publisher, or other rightsholder or rightsholder partner exercises a legal monopoly afforded by modern copyright and i ...
.


Overview

Allman had written the original
ARPANET The Advanced Research Projects Agency Network (ARPANET) was the first wide-area packet-switched network with distributed control and one of the first networks to implement the TCP/IP protocol suite. Both technologies became the technical fou ...
delivermail The ancestor of sendmail, delivermail, also by Eric Allman, is a mail transport agent that used the FTP protocol on the early ARPANET to transmit e-mail to the recipient. Due to deficiencies in using FTP to send e-mail, a new protocol was created ...
which shipped in 1979 with 4.0 and 4.1 BSD. He wrote Sendmail as a derivative of delivermail in the early 1980s at
UC Berkeley The University of California, Berkeley (UC Berkeley, Berkeley, Cal, or California) is a public land-grant research university in Berkeley, California. Established in 1868 as the University of California, it is the state's first land-grant uni ...
. It shipped with BSD 4.1c in 1983, the first BSD version that included TCP/IP protocols. In 1996, approximately 80% of the publicly reachable mail-servers on the Internet ran Sendmail. More recent surveys have suggested a decline, with 3.64% of mail servers in March 2021 detected as running Sendmail in a study performed by E-Soft, Inc. A previous survey (December 2007 or earlier) reported 24% of mail servers running Sendmail according to a study performed by Mail Radar. Allman designed Sendmail to incorporate great flexibility, but it can be daunting to configure for novices. Standard configuration packages delivered with the source code distribution require the use of the M4 macro language which hides much of the configuration complexity. The configuration defines the site-local mail delivery options and their access parameters, the mechanism of forwarding mail to remote sites, as well as many application tuning parameters. Sendmail supports a variety of mail transfer protocols, including
SMTP The Simple Mail Transfer Protocol (SMTP) is an Internet standard communication protocol for electronic mail transmission. Mail servers and other message transfer agents use SMTP to send and receive mail messages. User-level email clients ty ...
, DECnet's
Mail-11 {{Unreferenced, date=December 2009 Mail-11 was the native email transport protocol used by Digital Equipment Corporation's OpenVMS, VMS operating system, and supported by several other DEC operating systems such as Ultrix. It normally used the Dec ...
, HylaFax, QuickPage and
UUCP UUCP is an acronym of Unix-to-Unix Copy. The term generally refers to a suite of computer programs and protocols allowing remote execution of commands and transfer of files, email and netnews between computers. A command named is one of the pr ...
. Additionally, Sendmail v8.12 introduced support for milters - external mail filtering programs that can participate in each step of the
SMTP The Simple Mail Transfer Protocol (SMTP) is an Internet standard communication protocol for electronic mail transmission. Mail servers and other message transfer agents use SMTP to send and receive mail messages. User-level email clients ty ...
conversation.


Acquisition by Proofpoint, Inc.

Sendmail, Inc was acquired by Proofpoint, Inc. This announcement was released on 1 October 2013.


Security

Sendmail originated in the early days of the Internet, an era when considerations of security did not play a primary role in the development of network software. Early versions of Sendmail suffered from a number of security vulnerabilities that have been corrected over the years. Sendmail itself incorporated a certain amount of
privilege separation In computer programming and computer security, privilege separation is one software-based technique for implementing the principle of least privilege. With privilege separation, a program is divided into parts which are limited to the specific pri ...
in order to avoid exposure to security issues. , current versions of Sendmail, like other modern MTAs, incorporate a number of security improvements and optional features that can be configured to improve security and help prevent abuse.


History of vulnerabilities

Sendmail vulnerabilities in CERT advisories and alerts: * * * * * * * * The '' UNIX-HATERS Handbook'' dedicated an entire chapter to perceived problems and weaknesses of sendmail.


Implementation

As of sendmail release 8.12.0 the default implementation of sendmail runs as the Unix user smmsp — the sendmail message submission program.


See also

*
List of mail servers This is a list of mail server software: mail transfer agents, mail delivery agents, and other computer software which provide e-mail. Product statistics All such figures are necessarily estimates because data about mail server share is diffi ...
*
Comparison of mail servers The comparison of mail servers covers mail transfer agents (MTAs), mail delivery agents, and other computer software that provide e-mail services. Unix-based mail servers are built using a number of components because a Unix-style environment i ...
*
Mail delivery agent A message delivery agent (MDA), or mail delivery agent, is a computer software component that is responsible for the delivery of e-mail messages to a local recipient's mailbox., ''Internet Mail Architecture'', D. Crocker (July 2009) It is also call ...
*
Mail user agent The mail or post is a system for physically transporting postcards, letters, and parcels. A postal service can be private or public, though many governments place restrictions on private systems. Since the mid-19th century, national postal syst ...
* msmtp *
Internet messaging platform An Internet messaging platform is any system on the Internet that exchanges messages for the purpose of human communications. Messaging platforms are considered one of few key Internet infrastructure elements. What used to be only referred to as e ...
* Morris worm * MeTA1


Notes


References

* — This is the Sendmail "bible" containing 1308 pages about Sendmail. It is also known a
"The Bat Book"
because of the picture on its cover. The 1st Edition was published in November 1993. * — A companion to ''sendmail, 3rd Edition'', this book documents the improvements in V8.13 in parallel with its release. * * * * * — presented at the USENIX Annual Technical Conference


External links


Sendmail, Inc.

Sendmail sources


SMTP Fast Exploding External Deliverer for Sendmail. * Daniel J. Bernstein

October 2001 * Mike Brodbelt

{{Email servers Message transfer agents Free email server software Free software programmed in C Companies based in Emeryville, California Email server software for Linux 1983 software