Installing and Administering Internet Services

Chapter 4 183

Installing and Administering sendmail

Sendmail and the LDAP Protocol

LDAP (Lightweight Directory Access Protocol) enables servers to share

static information. Combining sendmail and LDAP increases the speed

and efﬁciency at which network information is collected and displayed.

Sendmail supports the use of the LDAP protocol to look up addresses.

The ldapx class, which is a database, is used to look up items in the ldap

directory service. The sendmail conﬁguration ﬁle contains the syntax

required, which is:

kname ldapx -k “uid=%s” -v“mail” -h“ldap_server_name” -b

“o=organization, c=US”

This enables the LDAP protocol to perform lookups. These lookups are

deﬁned entirely by the switches speciﬁed. In the syntax example above,

-k and -v are the switch options.

The -k switch deﬁnes how the map takes its input value and constructs

the LDAP search. The -v switch is the value that replaces the original

string in the map. In most cases, this will be an email address. The -b

switch is the “Directory” in the ldap “tree” where searching begins. The

-h switch is the space separated string of servers that support LDAP at

your site.

NOTE The “ldap-style” (-v and -h in theexample above) options must be double

quoted and must follow immediately after the option. There are no

spaces between the option and the quote.

Enabling Address Lookups Using LDAP

When you enable LDAp suppoet, LDAP will look up login names, then

return the email address for that user. To enable this, you must modify

the following lines in the sendmail.cf ﬁle. Here is how to enable

address lookup using LDAP:

1. Open the sendmail.cf ﬁle.

2. Uncomment the following ruleset: