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This article is about the mail transfer agent. For the company, see Sendmail, Inc..
Sendmail small logo.gif
Developer(s) Sendmail Consortium, Sendmail, Inc.
Stable release 8.15.2 Release Notes / July 3, 2015 (2015-07-03)
Operating system Cross-platform
Type Mail transfer agent
License Sendmail License
Developer(s) Claus Aßmann
Stable release / May 25, 2014 (2014-05-25)
Operating system Cross-platform
Type Mail transfer agent
License Sendmail License

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. It has spread both as free software and proprietary software.


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 in the early 1980s at UC Berkeley. 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.[1] More recent surveys have suggested a decline, with 8.86% of mail servers in April 2014 detected as running Sendmail in a study performed by E-Soft, Inc.[2]

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 Mail-11, HylaFax, QuickPage and UUCP. Additionally, Sendmail v8.12 as of September 2001 introduced support for milters - external mail filtering programs that can participate in each step of the SMTP conversation.

New development[edit]

The next generation of Sendmail was initially called Sendmail X; it was previously 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- 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.

MeTA1 was released on May 25, 2014.

Acquisition by Proofpoint, Inc.[edit]

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

Sendmail 8 releases[edit]

The information derives from RELEASE_NOTES file from sendmail distribution.


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.[citation needed] 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, 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[edit]

Sendmail vulnerabilities in CERT advisories and alerts:

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


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

See also[edit]


  1. ^ D. J. Bernstein (1996-11-27). "Internet host SMTP server survey". 
  2. ^ "E-Soft MX survey". 
  3. ^ "Sendmail Installation and Operations Guide" (PDF). 
  4. ^ "Sendmail release notes". The Sendmail Consortium. Retrieved 2009-08-30. 


  • Bryan Costales with Eric Allman (October 2007). sendmail, 4th Edition. O'Reilly and Associates.  — This is the Sendmail "bible" containing 1308 pages about Sendmail. It is also known as "The Bat Book", because of the picture on its cover. The 1st Edition was published in November 1993.
  • Bryan Costales, George Jansen, Claus Assmann, Gregory Shapiro (September 2004). sendmail 8.13 Companion. O'Reilly and Associates.  — A companion to sendmail, 3rd Edition, this book documents the improvements in V8.13 in parallel with its release.
  • Craig Hunt (December 2003). sendmail Cookbook. O'Reilly. 
  • Nick Christenson (2002-09-13). sendmail Performance Tuning. Addison-Wesley.  [1]

External links[edit]