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 MDA software for Unix-like platforms

• Cyrus IMAP - A mail server suite that includes a mail delivery agent
• dovecot - A mail server suite that includes a mail delivery agent
• fdm (e-mail utility) - A combined mail retrieval agent and mail delivery agent - for complex mail sorting, the man page refers users to maildrop
• fetchmail - mpop is a faster more modern fetchmail alternative, these are primarily mail retrieval programs
• mailagent - an MDA with manual config for many parameters such as timezone; seems to have a Debian package at least.
• maildrop or courier-maildrop (same program?) - traditional procmail replacement
• postdrop or postfix-maildrop (same program?) - A mail delivery agent for use with the postfix mail transport agent; see also the Postfix daemons smtp, local, virtual (?).
• sieve - a more modern replacement for procmail from the GNU Mailutils package

Obsolete MDA software for Unix-like platforms

• bin/mail, the MDA part of Sendmail - Sendmail is one of the oldest email packages
• 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. Old? That URL refers to a web service today it seems.
• dystill - A filtering MySQL database driven mail delivery agent - obsolete or old, no Debian package.
• procmail - obsolete since it's unmaintained; old, but still used

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