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LDAP server to look up a particular email address from a common corporate directory by a user's last
name. In this kind of implementation, LDAP is largely separate from Sendmail, with LDAP storing
the hierarchical user information and Sendmail only being given the result of LDAP queries in pre-
addressed email messages.
However, Sendmail supports a much greater integration with LDAP, where it uses LDAP to replace
separately maintained files, such as aliases and virtusertables, on different mail servers that
work together to support a medium- to enterprise-level organization. In short, you can use LDAP to
abstract the mail routing level from Sendmail and its separate configuration files to a powerful LDAP
cluster that is being leveraged by many different applications.
The current version of Sendmail contains support for LDAP. To extend your Sendmail server using
LDAP, first get an LDAP server, such as OpenLDAP, running and properly configured. Then, you
need to edit your /etc/mail/sendmail.mc to include:
Figure 16–5 Example settings for LDAP in sendmail.mc
LDAPROUTE_DOMAIN(' yourdomain.com ')dnl
FEATURE('ldap_routing')dnl
This is only for a very basic configuration of Sendmail with LDAP. Your con-
figuration should differ greatly from this depending on your implementation
of LDAP, especially if you wish to configure several Sendmail machines to
use a common LDAP server.
Consult /usr/share/doc/sendmail/README.cf for detailed
LDAP routing configuration instructions and examples.
Next, recreate your /etc/sendmail.cf file by running m4 and restarting Sendmail. See Section
16.3.4, Common Sendmail Configuration Changes for instructions on doing this.
For more information on LDAP, see Chapter 15, Lightweight Directory Access Protocol (LDAP).
16.4 Fetchmail
Fetchmail is a program that can retrieve email from remote servers for on-demand TCP/IP connections.
Many users appreciate the ability to separate the process of downloading their messages located on
a remote server from the process of reading and organizing their email in an MUA. Designed with
the needs of dial-up users in mind, Fetchmail will connect and quickly download all of your email
messages to your mail spool file using any number of protocols, including the POP3 and IMAP. It can
even forward your email messages to an SMTP server, if necessary.
Note
Chapter 16:Email
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