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208 Chapter 16. Email

Because /etc/mail/access.db is a database, you need to use makemap to activate your

changes by recreating the database map. This is easily done by running the makemap hash

/etc/mail/access

/etc/mail/access command as root.

This example shows that any email sent from badspammer.com would be blocked with a 550

RFC-821 compliant error code and message back to the spammer, except for email sent from the

tux.badspammer.com sub-domain, which would be accepted. The last line shows that any email

sent from the 10.0.*.* network can be relayed through your mail server.

As you might expect, this example only scratches the surface of what Sendmail can do in terms of

allowing or blocking access. See the /usr/share/doc/sendmail/README.cf for more detailed

information and examples.

16.3.6. 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, you could use an

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:

LDAPROUTE_DOMAIN(’yourdomain.com’)dnl

FEATURE(’ldap_routing’)dnl

Figure 16-5. Example settings for LDAP in sendmail.mc

Note

This is only for a very basic conﬁguration of Sendmail with LDAP. Your conﬁguration 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 for instructions on doing this.

For more information on LDAP, see Chapter 19.

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Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE Guida di Installazione Pagina 208