Red Hat ENTERPRISE LINUX 4.5.0 Reference Manual page 217

Sendmail
Now, however, Sendmail must be configured to permit any domain to relay mail through the
server. To configure relay domains, edit the file and restart
/etc/mail/relay-domains
Sendmail.
However, many times users are bombarded with spam from other servers throughout the
Internet. In these instances, Sendmail's access control features available through the
file can be used to prevent connections from unwanted hosts. The following
/etc/mail/access
example illustrates how this file can be used to both block and specifically allow access to the
Sendmail server:
badspammer.com ERROR:550 "Go away and do not spam us anymore"
tux.badspammer.com OK 10.0 RELAY
This example shows that any email sent from is blocked with a 550 RFC-821
badspammer.com
compliant error code, with a message sent back to the spammer. Email sent from the
sub-domain, is accepted. The last line shows that any email sent from the
tux.badspammer.com
10.0.*.* network can be relayed through the mail server.
Because is a database, use to activate any changes. Do this
/etc/mail/access.db makemap
using the following command as root:
makemap hash /etc/mail/access < /etc/mail/access
This example only represents a small part of what Sendmail can do in terms of allowing or
blocking access. Refer to the for more information and
/usr/share/sendmail-cf/README
examples.
Since Sendmail calls the Procmail MDA when delivering mail, it is also possible to use a spam
filtering program, such as SpamAssassin, to identify and file spam for users. Refer to
Section 4.2.6, "Spam Filters" for more about using SpamAssassin.
3.1.6. Using Sendmail with LDAP
Using the Lightweight Directory Access Protocol (LDAP) is a very quick and powerful way to find
specific information about a particular user from a much larger group. For example, an LDAP
server can be used to look up a particular email address from a common corporate directory by
the 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 and , on different mail
aliases virtusertables
servers that work together to support a medium- to enterprise-level organization. In short, LDAP
abstracts the mail routing level from Sendmail and its separate configuration files to a powerful
LDAP cluster that can be leveraged by many different applications.
The current version of Sendmail contains support for LDAP. To extend the Sendmail server
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