Sendmail headquarters in Emeryville (in the same building as Jamba Juice).

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.

[edit] Overview

Allman had written the original ARPANET 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.

Sendmail is the most popular mail transfer agent (MTA) on the Internet.^{[citation needed]} Its popularity is due in part to its position as the standard MTA under most variants of the Unix and other Unix-like operating system.^{[citation needed]}

In 2001, approximately 42% of the publicly-reachable mail-servers on the Internet ran Sendmail.^[1] 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.^[2] 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.^[3] 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 mail11, HylaFax, QuickPage and UUCP. Additionally, Sendmail v8.12 as of September 2001^[update] introduced support for milters - external mail filtering programs that can participate in each step of the SMTP conversation.

[edit] 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.

As of October 2008^[update] development on MeTA1 continues, with the released code at the pre-alpha stage.

[edit] Sendmail 8 releases

• 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.

[edit] 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 order to avoid exposure to security issues. As of 2009^[update], 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.

[edit] History of vulnerabilities

Sendmail vulnerabilities in CERT advisories and alerts:

• "TA06-081A Sendmail Race Condition Vulnerability". US-CERT Alerts. http://www.us-cert.gov/cas/techalerts/TA06-081A.html. 
• "CA-2003-25 Buffer Overflow in Sendmail". CERT Advisories. http://www.cert.org/advisories/CA-2003-25.html. Retrieved January 7, 2005. 
• "CA-2003-12 Buffer Overflow in Sendmail". CERT Advisories. http://www.cert.org/advisories/CA-2003-12.html. Retrieved January 7, 2005. 
• "CA-2003-07 Remote Buffer Overflow in Sendmail". CERT Advisories. http://www.cert.org/advisories/CA-2003-07.html. Retrieved January 7, 2005. 
• "CA-1997-05 MIME Conversion Buffer Overflow in Sendmail Versions 8.8.3 and 8.8.4". CERT Advisories. http://www.cert.org/advisories/CA-1997-05.html. Retrieved January 7, 2005. 
• "CA-1996-25 Sendmail Group Permissions Vulnerability". CERT Advisories. http://www.cert.org/advisories/CA-1996-25.html. Retrieved January 7, 2005. 
• "CA-1996-24 Sendmail Daemon Mode Vulnerability". CERT Advisories. http://www.cert.org/advisories/CA-1996-24.html. Retrieved January 7, 2005. 
• "CA-1996-20 Sendmail Vulnerabilities". CERT Advisories. http://www.cert.org/advisories/CA-1996-20.html. Retrieved January 7, 2005. 

The original UNIX-HATERS Handbook dedicated an entire chapter to perceived problems and weaknesses of sendmail.

[edit] Implementation

As of sendmail release 8.12.0 the default implementation of sendmail runs as the Unix user smmsp^[4] — the sendmail message submission program.

[edit] See also

• List of mail servers
• Mail delivery agent
• Mail user agent
• Internet messaging platform
• Morris worm

[edit] Footnotes

[edit] References

[edit] External links

• Sendmail Consortium, sendmail.org
• Sendmail, Inc., sendmail.com
• Bryan Costales, George Jansen and Claus Aßmann with Gregory Neil Shapiro Sendmail, 4th Edition, O'Reilly, October 2007, ISBN-13: 978-0-596-51029-9
• Milter.org, Sendmail MILTERs [2]
• Daniel J. Bernstein, Internet SMTP server survey, October 2001
• Mike Brodbelt, A brief history of mail
• Lourier, Philippe (1999). "History of Sendmail: Interview with Eric Allman". Dr. Dobb's Journal. http://technetcast.ddj.com/tnc_program.html?program_id=32. 
• Eric Allman et al. (1999) (PDF). Sendmail Evolution: 8.10 and Beyond. http://www.sendmail.org/~gshapiro/Sendmail-8.10.Paper.pdf.  — presented at the USENIX Annual Technical Conference
• Williamson, Alan (2003-08-11). "A Talk with the Father of sendmail". LinuxWorld. http://linux.sys-con.com/read/33904.htm.