Sidebar: About sendmail 8.6.9

sendmail is used for processing both incoming and outgoing mail. You can download the source code for sendmail 8.6.9 by anonymous ftp from a number of sites. This software's home is:

ftp.cs.berkeley.edu:/ucb/src/sendmail

In this directory you will find the following files related to sendmail 8.6.9:

500945 Apr 19  1994 sendmail.8.6.9.base.tar.gz
199863 Apr 19  1994 sendmail.8.6.9.cf.tar.gz
106149 Apr 19  1994 sendmail.8.6.9.misc.tar.gz
130419 Apr 19  1994 sendmail.8.6.9.patch
306207 Apr 19  1994 sendmail.8.6.9.xdoc.tar.gz

You can download these files and build them, using the Makefile for your platform.

This version of sendmail is, according to our information at least, the most current one. It fixes a number of bugs and security holes from previous versions, notably sendmail 5.6.x, which is still part of some commercial UNIX versions.

sendmail is often called an MTA (Mail Transfer Agent). It transports mail. During this transport a number of headers in the message may need to be transformed from one form to another. This transformation may be necessary due to restrictions imposed by the delivery protocol. For instance, UUCP normally uses a bang path (!) to separate the user from the node. SMTP can use the familiar @ symbol. Failing to comply with these conventions may render your mail undeliverable.

Depending on a number of factors, sendmail selects a delivery agent, which takes care of the actual delivery of the message. sendmail doesn't do any delivery at all. The delivery agent has all the knowledge about the delivery process. You can, for instance, write your own delivery agent to support a special protocol.

The selection process is controlled by the rewrite rule sets in the configuration file. Rewrite rule sets specify how to transform an address from one form to another. Rules are specified in a special format resembling regular expressions. Different rule sets are used for different fields in the message header.

It is possible to configure the rule sets completely by hand. sendmail 8 supports another way, however. In sendmail's source directory tree is a special subdirectory for configuring sendmail. It contains a number of M4 (macro processor) files that can be used to implement different functions in the configuration file. By using these standard functions, you can create a configuration quickly and reliably.

To learn more about sendmail, read the book sendmail, by Brian Costales, with Eric Allman and Neil Rickert, published by O'Reilly and Associates ("The BatBook"). It covers all aspects of sendmail, including configuring the different versions.