Mail delivery agent

A mail delivery agent or message delivery agent (MDA) is a computer software component that is responsible for the delivery of e-mail messages to a local recipient's mailbox.^[1] Also called an LDA, or local delivery agent.^[2]

Within the Internet mail architecture, local message delivery is achieved through a process of handling messages from the message transfer agent, and storing mail into the recipient's environment (typically a mailbox).

Implementation

Many Mail Handling Software products bundle multiple message delivery agents with the message transfer agent component, providing for site customization of the specifics of mail delivery to a user.

Unix

On Unix-like systems, procmail and maildrop are the most popular MDAs. The Local Mail Transfer Protocol (LMTP) is a protocol that is frequently implemented by network-aware MDAs.

Invocation

The mail delivery agent is generally not started from the command line, but is usually invoked by mail delivery subsystems, such as a mail transport agent, or a mail retrieval agent.

List of message delivery agent software for Unix-like platforms

• bin/mail, the MDA part of Sendmail
• deliver
• fdm - A combined mail retrieval agent and mail delivery agent
• Fetchmail
• maildrop
• postdrop
• postfix-maildrop - A mail delivery agent for use with the postfix mail transport agent
• smtp, local, virtual - Postfix daemons
• procmail
• courier-maildrop
• dovecot - A mail server suite that includes a mail delivery agent
• DBMail - MDA written in C by Eelco van Beek and Roel Rozendaal. Provides IMAP and POP3 daemons that use a MySQL or PostgreSQL mail store.
• dystill - A filtering MySQL database driven mail delivery agent
• Cyrus IMAP - A mail server suite that includes a mail delivery agent

See also

• Message transfer agent (MTA)
• Mail retrieval agent (MRA)
• Mail submission agent (MSA)
• Mail user agent (MUA) a.k.a. email client
• E-mail agent (infrastructure) (MxA)

References

1. RFC 5598, Internet Mail Architecture, D. Crocker (July 2009)
2. Dovecot (software)