Editing Sendmail (section)

==Overview==
Allman wrote 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.<ref>{{Cite web
|author=D. J. Bernstein
|url=http://cr.yp.to/surveys/smtpsoftware.txt
| archive-url=https://ghostarchive.org/archive/20211024/http://cr.yp.to/surveys/smtpsoftware.txt
| archive-date=2021-10-24|title=Internet host SMTP server survey
|date=1996-11-27
}}{{cbignore}}
</ref> 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.<ref>{{Cite web
|url=http://www.securityspace.com/s_survey/data/man.202102/mxsurvey.html
| archive-url=https://ghostarchive.org/archive/20211024/http://www.securityspace.com/s_survey/data/man.202102/mxsurvey.html
| archive-date=2021-10-24|title=E-Soft MX survey |website=securityspace.com |publisher=E-Soft Inc. |date=1 March 2021 |access-date=21 March 2021
}}{{cbignore}}</ref>  A previous survey (December 2007 or earlier) reported 24% of mail servers running Sendmail according to a study performed by Mail Radar.<ref>{{Cite web
 |url         = http://www.mailradar.com/mailstat/
 |title       = Mail Radar survey
 |url-status     = dead
 |archive-url  = https://web.archive.org/web/20071213001115/http://www.mailradar.com:80/mailstat/
 |archive-date = 2007-12-13
}}</ref>

Allman designed Sendmail to incorporate great flexibility, but it can be daunting to configure for novices.<ref>{{Cite web
|url=http://www.sendmail.org/doc/sendmail-current/doc/op/op.pdf
|title=Sendmail Installation and Operations Guide
|first1=Eric|last1=Allman
|first2=Claus|last2=Assmann
|first3=Gregory Neil|last3=Shapiro
|archive-url=https://web.archive.org/web/20081203001718/http://www.sendmail.org/doc/sendmail-current/doc/op/op.pdf|archive-date=2008-12-03
|access-date=2009-07-28
}}</ref> Standard configuration packages delivered with the source code distribution require the use of the [[M4 (computer language)|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 protocol]]s, including [[SMTP]], [[DECnet]]'s [[Mail-11]], [[HylaFAX]], QuickPage and [[UUCP]]. Additionally, Sendmail v8.12 {{As of|2001|alt=as of September 2001}} introduced support for [[milter]]s - external mail filtering programs that can participate in each step of the [[SMTP]] conversation.