Sendmail
Encyclopedia
Sendmail is a general purpose internetwork email
routing facility that supports many kinds of mail-transfer and -delivery methods, including the Simple Mail Transfer Protocol
(SMTP) used for email transport over the Internet
.
A descendant of the delivermail
program written by Eric Allman
, Sendmail is a well-known project
of the free and open source software
and Unix
communities, and has spread both as free software
and proprietary software
. Greg Olson incorporated the company and drove sales in the early years. When sales went flat in Europe, he took charge of the territory and European sales resumed their brisk pace. He served as Sendmail's CEO for a time.
delivermail
which shipped in 1979 with 4.0 and 4.1 BSD. He wrote Sendmail as a derivative of delivermail early in the 1980s at UC Berkeley. It shipped with BSD 4.1c in 1983, the first BSD version that included TCP/IP protocols.
In 2001, approximately 42% of the publicly-reachable mail-servers on the Internet ran Sendmail. More recent surveys have suggested a decline, with 29.4% of mail servers in August 2007 detected as running Sendmail in a study performed by E-Soft, Inc. Sendmail is trailed by Microsoft Exchange Server
, Exim
, and Postfix
; these four being the only mail servers with more than 10% of the total.
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, ESMTP, DECnet
's Mail-11
, HylaFax, QuickPage and UUCP
. Additionally, Sendmail v8.12 introduced support for milter
s - external mail filtering programs that can participate in each step of the SMTP conversation.
The first release of Sendmail X (smX-0.0.0.0) was made available on October 30, 2005. The final release was smX-1.0.PreAlpha7.0., released on May 20, 2006 under the same license used by Sendmail 8.
development on MeTA1 continues, with the released code at the alpha stage.
The information derives from RELEASE_NOTES file from sendmail distribution.
Sendmail itself incorporated a certain amount of privilege separation
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.
The UNIX-HATERS Handbook dedicated an entire chapter to perceived problems and weaknesses of sendmail.
Email
Electronic mail, commonly known as email or e-mail, is a method of exchanging digital messages from an author to one or more recipients. Modern email operates across the Internet or other computer networks. Some early email systems required that the author and the recipient both be online at the...
routing facility that supports many kinds of mail-transfer and -delivery methods, including the Simple Mail Transfer Protocol
Simple Mail Transfer Protocol
Simple Mail Transfer Protocol is an Internet standard for electronic mail transmission across Internet Protocol networks. SMTP was first defined by RFC 821 , and last updated by RFC 5321 which includes the extended SMTP additions, and is the protocol in widespread use today...
(SMTP) used for email transport over the Internet
Internet
The Internet is a global system of interconnected computer networks that use the standard Internet protocol suite to serve billions of users worldwide...
.
A descendant of the delivermail
Delivermail
The ancestor of sendmail, delivermail is a mail transport agent that used the FTP protocol on the early ARPANET to transmit e-mail to the recipient....
program written by Eric Allman
Eric Allman
Eric Paul Allman is an American computer programmer who developed sendmail and its precursor delivermail in the late 1970s and early 1980s at UC Berkeley.-Education and training:...
, Sendmail is a well-known project
Project
A project in business and science is typically defined as a collaborative enterprise, frequently involving research or design, that is carefully planned to achieve a particular aim. Projects can be further defined as temporary rather than permanent social systems that are constituted by teams...
of the free and open source software
Free and open source software
Free and open-source software or free/libre/open-source software is software that is liberally licensed to grant users the right to use, study, change, and improve its design through the availability of its source code...
and Unix
Unix
Unix is a multitasking, multi-user computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs, including Ken Thompson, Dennis Ritchie, Brian Kernighan, Douglas McIlroy, and Joe Ossanna...
communities, and has spread both as free software
Free software
Free software, software libre or libre software is software that can be used, studied, and modified without restriction, and which can be copied and redistributed in modified or unmodified form either without restriction, or with restrictions that only ensure that further recipients can also do...
and proprietary software
Proprietary software
Proprietary software is computer software licensed under exclusive legal right of the copyright holder. The licensee is given the right to use the software under certain conditions, while restricted from other uses, such as modification, further distribution, or reverse engineering.Complementary...
. Greg Olson incorporated the company and drove sales in the early years. When sales went flat in Europe, he took charge of the territory and European sales resumed their brisk pace. He served as Sendmail's CEO for a time.
Overview
Allman had written the original ARPANETARPANET
The Advanced Research Projects Agency Network , was the world's first operational packet switching network and the core network of a set that came to compose the global Internet...
delivermail
Delivermail
The ancestor of sendmail, delivermail is a mail transport agent that used the FTP protocol on the early ARPANET to transmit e-mail to the recipient....
which shipped in 1979 with 4.0 and 4.1 BSD. He wrote Sendmail as a derivative of delivermail early in the 1980s at UC Berkeley. It shipped with BSD 4.1c in 1983, the first BSD version that included TCP/IP protocols.
In 2001, approximately 42% of the publicly-reachable mail-servers on the Internet ran Sendmail. More recent surveys have suggested a decline, with 29.4% of mail servers in August 2007 detected as running Sendmail in a study performed by E-Soft, Inc. Sendmail is trailed by Microsoft Exchange Server
Microsoft Exchange Server
Microsoft Exchange Server is the server side of a client–server, collaborative application product developed by Microsoft. It is part of the Microsoft Servers line of server products and is used by enterprises using Microsoft infrastructure products...
, Exim
Exim
Exim is a mail transfer agent used on Unix-like operating systems. Exim is free software distributed under the terms of the GNU General Public License, and it aims to be a general and flexible mailer with extensive facilities for checking incoming e-mail....
, and Postfix
Postfix (software)
In computing, Postfix is a free and open-source mail transfer agent that routes and delivers electronic mail. It is intended as a fast, easier-to-administer, and secure alternative to the widely-used Sendmail MTA....
; these four being the only mail servers with more than 10% of the total.
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
M4 (computer language)
m4 is a general purpose macro processor designed by Brian Kernighan and Dennis Ritchie. m4 is an extension of an earlier macro processor m3, written by Ritchie for the AP-3 minicomputer.-Use:...
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, ESMTP, DECnet
DECnet
DECnet is a suite of network protocols created by Digital Equipment Corporation, originally released in 1975 in order to connect two PDP-11 minicomputers. It evolved into one of the first peer-to-peer network architectures, thus transforming DEC into a networking powerhouse in the 1980s...
's Mail-11
Mail-11
Mail-11 was the native email transport protocol used by Digital Equipment Corporation's VMS operating system, and supported by several other DEC operating systems such as Ultrix.It normally used the DECnet networking system as opposed to TCP/IP....
, HylaFax, QuickPage and UUCP
UUCP
UUCP is an abbreviation for 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. Specifically, a command named uucp is one of the programs in the suite; it...
. Additionally, Sendmail v8.12 introduced support for milter
Milter
Milter is an extension to the widely used open source mail transfer agents Sendmail and Postfix. It allows administrators to add mail filters for filtering spam or viruses very efficiently in the mail-processing chain...
s - external mail filtering programs that can participate in each step of the SMTP conversation.
New development
The next generation of Sendmail was initially called Sendmail X, previously it was called Sendmail 9, but it does not derive from the Sendmail version 8 code base. However, the development of Sendmail X was stopped in favor of a new project called MeTA1.The first release of Sendmail X (smX-0.0.0.0) was made available on October 30, 2005. The final release was smX-1.0.PreAlpha7.0., released on May 20, 2006 under the same license used by Sendmail 8.
development on MeTA1 continues, with the released code at the alpha stage.
Sendmail 8 releases
- Sendmail-8.14.5 2011-05-17
- Sendmail-8.14.4 2009-12-30
- Sendmail-8.14.3 2008-05-03
- Sendmail-8.14.2 2007-11-01
- Sendmail-8.14.1 2007-04-03
- Sendmail-8.14.0 2007-01-31
- Sendmail-8.13.0 2004-06-20
- Sendmail-8.12.0 2001-09-08
- Sendmail-8.11.0 2000-07-19
- Sendmail-8.10.0 2000-03-01
- Sendmail-8.9.0 1998-05-19
- Sendmail-8.8.0 1996-09-26
- Sendmail-8.7 1995-09-16
- Sendmail-8.6 1993-10-05
- ...
- Sendmail-8.1 1993-06-07 - 4.4BSD freeze. No semantic changes.
The information derives from RELEASE_NOTES file from sendmail distribution.
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
Privilege separation
In computer programming and computer security, privilege separation is a technique in which a program is divided into parts which are limited to the specific privileges they require in order to perform a specific task...
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
- Mail delivery agentMail delivery agentA mail delivery agent or message delivery agent is a computer software component that is responsible for the delivery of e-mail messages to a local recipient's mailbox...
- Mail user agent
- Internet messaging platform
- Morris worm
External links
- Sendmail Consortium
- Sendmail, Inc.
- Bryan Costales, George Jansen and Claus Aßmann with Gregory Neil Shapiro Sendmail, 4th Edition, O'ReillyO'ReillyO'Reilly is the Anglicised form of the Gaelic Ó Raghallaigh. It is also the patronymic form of the Irish name Reilly . It is commonly found throughout Ireland, with the greatest concentration of the surname found in County Cavan followed by Longford, Meath, Westmeath, Fermanagh and Monaghan, and...
, October 2007, ISBN 978-0-596-51029-9 - Milter.org, Sendmail MILTERs http://www.milter.org
- Daniel J. Bernstein, Internet SMTP server survey, October 2001
- Mike Brodbelt, A brief history of mail — presented at the USENIXUSENIX-External links:* *...
Annual Technical Conference