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This is the Title of the Book, eMatter Edition
Copyright ?© 2007 O??™Reilly & Associates, Inc. All rights reserved.
4 | Chapter 1: Some Basics
The sendmail program needs to transport mail between a wide variety of machines.
Consequently, its configuration file is designed to be very flexible. This concept
allows a single binary to be distributed to many machines, where the configuration
file can be customized to suit particular needs. This configurability contributes to
making sendmail complex.
When mail needs to be delivered to a particular user, for example, the sendmail program
decides on the appropriate delivery method based on its configuration file. The
decision process might include the following steps:
??? If the recipient receives mail on the same machine as the sender, sendmail delivers
the mail using the /usr/sbin/mail.local program.
??? If the recipient??™s machine is connected to the sending machine using UUCP, it
uses uux to send the mail message.
??? If the recipient??™s machine is on the Internet, the sending machine transports the
mail using SMTP.
??? Otherwise, the mail message might need to be transported over another network
(such as Bitnet) or possibly rejected.
1.4 Basic Parts of sendmail
The sendmail program is actually composed of several parts, including programs,
files, directories, and the services it provides.
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