20.4 Delivery Agents by Name As we have shown earlier, the MAILER command is used to enable a class of delivery agents. For example: MAILER(`smtp') This command causes support for the smtp , esmtp , smtp8 , dsmtp , and relay delivery agents to be included in your configuration file. Further, the confSMTP_MAILER mc configuration macro can be used to define which one you want to use as your default outbound delivery agent: define(`confSMTP_MAILER', `dsmtp') Before you can choose a default, however, you need to know what each delivery agent does and how they differ . In this section, we describe these and all the other standard and special delivery agents. We describe them in alphabetical order, with a convenient summary shown in Table 20-1. Table 20-1. Delivery agents described by name MAILER( ) | Agents declared | Description | cyrus | cyrus and cyrusbb (cyrus) | Deliver to a local cyrus user . Handles user+where@local.host syntax to the user's IMAP Vmailbox. | cyrusv2 | cyrusv2 (cyrusv2) | Somewhat like cyrus , but delivers using LMTP via a Unix-domain socket, and requires Cyrus V2. | none | discard (discard) | Causes the message to be accepted and discarded. | none | error (error) | Causes the message to be rejected. | fax | fax (fax) | Delivers to a program that handles fax delivery. | none | * file * and * include * (*file* and *include*) | Performs delivery by appending to a file, and handle delivery through :include: lists. | local | local (See this section), prog (See this section) | Performs final, local delivery, either to a user's mailbox or through a program. | mail11 | mail11 (mail11) | Allows use of the mail11 program for delivery to DECnet addresses. | phquery | ph (ph) | Delivery is through the phquery program, which looks up user information in the CCSO nameserver database, and then provides appropriate information for delivery (deprecated). | pop | pop (pop) | Delivery for POP users who lack local accounts using MH's spop . | procmail | procmail (procmail) | Delivers via procmail , which allows additional processing for local or special delivery needs. | qpage | qpage (qpage) | Part of a client/server software package that allows messages to be sent via an alphanumeric pager. | smtp | smtp (smtp, etc.), esmtp (See this section), smtp8 (See this section), dsmtp (See this section), and relay (See this section), | The internal SMTP delivery agents. | usenet | usenet (usenet) | The usenet delivery agent is used to post messages to the USENET by means of the inews program. | uucp | uucp (Section 4.6.1), uucp-old (Section 4.6.1), uucp-new (Section 4.6.2), suucp (Section 4.6.2), uucp-dom (Section 4.6.3), uucp-uudom (Section 4.6.4) | The delivery agents used to send UUCP mail. | |