sendmail, 4th Edition

Relaying

Promiscuous relaying is the process of accepting email from outside your site and then transmitting it to another host also outside your site. Hosts that relay are quickly discovered by spam programs and are used to mask the identity of the originating spam site. Prior to V8.9, promiscuous relaying was allowed by default. Beginning with V8.9, promiscuous relaying is turned off by default.

In place of default relaying, V8.9 and later sendmail provide a variety of features, macros, and databases that allow you to relay in a variety of manners. The access database (The access Database on page 277) provides a way to relay on a host-by-host, or network basis. Adding domains to the class $=R ($=R on page 874) is another method. In this section, we describe features that allow you to tune relaying to your taste. Table 7-2 lists the features available as of V8.12.

Table 7-2. Relay features

Feature	§	Description
access_db	The access Database on page 277	Screen addresses and set policy.
loose_relay_check	FEATURE(loose_relay_check) on page 270	Allow %-hack relaying.
promiscuous_relay	FEATURE(promiscuous_relay) on page 271	Allow all relaying.
relay_based_on_MX	FEATURE(relay_based_on_MX) on page 271	Relay for any site for which you are an MX server.
relay_entire_domain	FEATURE(relay_entire_domain) on page 272	Relay based on $=m.
relay_hosts_only	FEATURE(relay_hosts_only) on page 273	Interpret domains in relay domains, and access database, as hosts.
relay_local_from ...