Craig Hunt - sendmail Cookbook

To Amanda, Pat, Kathy, Sara, and all mothers everywhere who continue to renew life and our love of life.

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To follow a recipe successfully, you must clearly understand theinstructions it contains. You must understand the difference betweenfolding and stirring and be able to find the spices when the recipecalls for a pinch of cumin. Just as you must be able to find your wayaround the kitchen to become a cook, you must know your way aroundthe sendmail distribution in order to build or customize a sendmailconfiguration.

The directory

[1] Most of the ls command output in this book is generated on a Red Hat Linux system.Other versions of Unix and Linux may sort ls output in a different way. The listing order may be different, butthe files and directories will be the same.

Most of these files and directories are used to compile is in thesendmail directory, the libraries are indirectories such as libsm andlibsmutil, and the source code of utilities suchas makemap and smrsh islocated in easily identified directories.

There are also several important sources of information in thedistribution:

• The INSTALLand README filesprovide the latest information on compiling and installing sendmail.

• The RELEASE_NOTES file lists the importantfeatures of the new release.

• The KNOWNBUGS and FAQ files explainsolutions to chronic and common problems.

• The doc subdirectory contains the Sendmail Installation and Operations Guide ,which is an excellent source of information for the sendmailadministrator.

Of all of these important directories and files, the most important(from the perspective of this book) is the cfdirectory, because the cf directory contains theconfiguration files (and this is a book about sendmailconfiguration).

The m4 source files and libraries used to build thesendmail configuration are located in the cfdirectory, which contains the following items:

The cf directory contains two files,README and sendmail.schema,and nine subdirectories. The sendmail.schemafile isan experimental LDAP schema that predefines attribute types andobject classes that can be used with LDAP. The sendmail schema isused in most LDAP examples in this book. TheREADME fileis a comprehensive reference to the syntax and usage of all of the m4 macros and variables used to configuresendmail. The README file is an invaluablereference, particularly when used with this book.

The directories hack, sh,and siteconfig have very little use for mostconfigurations.

The hack directory is intended to holdm4 source files built by the local systemadministrator to solve temporary sendmail configuration problems.There is only one file in the hack directory,built years ago, which serves as an example of a sendmail hack. Thehack directory and the HACK macro are still there, but, with all of the power and flexibilityavailable to configure sendmail, there is simply no good reason touse them.

The siteconfig directory is intended to hold filesthat use sendmail m4 SITE macros to list the locally connected UUCP sites. Thesiteconfig directory, the SITECONFIG macro, and the SITE macro are maintained for backward compatibility. However, thedirectory and the macros are obsolete and should no longer be used todefine the UUCP connectivity for a UUCP mail server.