sendmail, 4th Edition

Relays

A relay is a rule that sends all of one type of mail to a specific destination. One example is email fax transmissions. Clearly, even though local mail should be delivered locally, mail to the pseudouser fax should always be sent to a special fax-handling machine.

The complete list of relays supported by the V8 sendmail mc technique is shown in Table 17-4.

Table 17-4. Relays

Relay	§	Versions	Description
BITNET_RELAY	BITNET_RELAY mc Macro on page 603	V8.1 and later	The BITNET relay
DECNET_RELAY	DECNET_RELAY mc Macro on page 604	V8.7 and later	The DECnet relay
FAX_RELAY	FAX_RELAY mc Macro on page 604	V8.6 and later	The FAX relay
LOCAL_RELAY	LOCAL_RELAY mc Macro on page 604	V8.1 and later	Relay for unqualified users
LUSER_RELAY	LUSER_RELAY mc Macro on page 605	V8.7 and later	Relay for unknown local users
MAIL_HUB	MAIL_HUB mc Macro on page 605	V8.6 and later	All local delivery on a central server
SMART_HOST	SMART_HOST mc macro on page 597	V8.6 and later	The ultimate relay
UUCP_RELAY	UUCP_RELAY mc Macro on page 606	V8.1 and later	The UUCP relay

All relays are declared in the same fashion. For example:

define(`LOCAL_RELAY',`agent:host')

Here, agent is the name of a delivery agent to use, and host is the name of the machine to which all such mail will be relayed. If agent: is missing, it defaults to a literal relay:.

If the host is listed under a domain that uses wildcard MX records (Wildcard MX Records on page 335), you should specify it with a trailing ...