Sendmail - Computer Definition
Widely used program that implements the SMTP mail delivery protocol on most UNIX and Linux systems. If someone’s ISP delivers email using SMTP, it is important to configure sendmail correctly to avoid “bouncing” email. If sendmail does not know a particular user name, it will reject the email and deliver the error message “550 User unknown.” As with regular land mail, when a recipient is not known because of a wrong or changed address, the land mail will be returned to the sender. The same principle applies to email. Bouncing wanted email is considered to be a beginner system administrator’s mistake by more seasoned experts, especially when it is from a mailing list.
Bouncing wanted email can occur when connecting UNIX to the Internet for the first time. These techniques can increase the chances that correctly addressed email is accepted by sendmail. Make sure that: any user name to which email is addressed is defined as a UNIX user, any name used on email is defined as an alias to UNIX users, and email addressed to unknown user names is redirected to defined UNIX users.
Kempston Webmaster.Solaris Resources at Kempston. [Online, February, 1, 2000.] Kempston Website. http://www.kempston.net/solaris/configsendmail2.html.
An SMTP-based message transfer agent (MTA) that runs under Unix. Developed at the University of California at Berkeley by Eric Allman in 1981, sendmail stores and forwards more mail than any other MTA on the Internet. In 1998, Allman commercialized the product by forming Sendmail, Inc. (www.sendmail.com), which offers a GUI interface for modifying the configuration file instead of dealing directly with more than a thousand lines of text. Sendmail, Inc. also offers a Windows version that includes the POP mail server and message store. Examples of mail clients developed for sendmail in the Unix world are elm, pine, mush and mailx. For information on the open source version, visit www.sendmail.org. See messaging system, BSD Unix and qmail.