A message delivery agent
), or mail delivery agent
, is a computer software
component that is responsible for the delivery of e-mail
messages to a local recipient's Email Mailbox
[, Internet Mail Architecture, D. Crocker (July 2009)]
It is also called a local delivery agent
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 Email Mailbox).
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.
are the most popular MDAs. The Local Mail Transfer Protocol (LMTP) is a protocol that is frequently implemented by network-aware MDAs.
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
fetchmail - Primarily a Mail retrieval agent (MRA)
getmail - simpler, more secure, modern fetchmail alternative
fdm — modern replacement for both fetchmail and procmail from the author of tmux
maildrop or courier-maildrop - traditional procmail replacement, part of Courier Mail Server, but can also be used with other mail servers
procmail - old, but still used
bin/mail, the MDA part of Sendmail - Sendmail is one of the oldest email packages
Sieve mail filtering language - a standardised mail filtering language; also, a modern replacement for procmail from the GNU Mailutils package
Message transfer agent (MTA)
Mail retrieval agent (MRA)
Message submission agent (MSA)
Message user agent (MUA) a.k.a. email client
E-mail agent (infrastructure) (MxA)