A message delivery agent (MDA), or mail delivery agent, is a computer
software
Software consists of computer programs that instruct the Execution (computing), execution of a computer. Software also includes design documents and specifications.
The history of software is closely tied to the development of digital comput ...
component that is responsible for the delivery of
e-mail
Electronic mail (usually shortened to email; alternatively hyphenated e-mail) is a method of transmitting and receiving Digital media, digital messages using electronics, electronic devices over a computer network. It was conceived in the ...
messages to a local recipient's
mailbox. It is also called a local delivery agent (LDA).
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).
Spam filtering usually occurs at the MDA under modern email architectures.
Implementation
Many mail handling software products bundle multiple message delivery agents with the
message transfer agent
Within the Internet email system, a message transfer agent (MTA), mail transfer agent, or mail relay is software that transfers electronic mail messages from one computer to another using the Simple Mail Transfer Protocol. In some contexts, the a ...
component, providing for site customization of the specifics of mail delivery to a user.
Unix
On
Unix-like
A Unix-like (sometimes referred to as UN*X, *nix or *NIX) operating system is one that behaves in a manner similar to a Unix system, although not necessarily conforming to or being certified to any version of the Single UNIX Specification. A Uni ...
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
Within the Internet email system, a message transfer agent (MTA), mail transfer agent, or mail relay is software that transfers electronic mail messages from one computer to another using the Simple Mail Transfer Protocol. In some contexts, the a ...
, or a
mail retrieval agent.
Unix-like
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Cyrus IMAP - A mail server suite that includes a mail delivery agent
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dovecot - A mail server suite that includes a mail delivery agent
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fetchmail - Primarily a
Mail retrieval agent (MRA)
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getmail - simpler, more secure, modern
fetchmail alternative
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fdm — modern replacement for both
fetchmail and
procmail from the author of
tmux
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maildrop or courier-maildrop - traditional procmail replacement, part of
Courier Mail Server
The Courier Mail Server is a mail transfer agent (MTA) server that provides Simple Mail Transfer Protocol, SMTP, IMAP, POP3, Simple Mail Access Protocol, SMAP, webmail, and electronic mailing list, mailing list services with individual components ...
, but can also be used with other mail servers
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procmail - old, but still used
* bin/mail, the MDA part of
Sendmail
Sendmail is a general purpose internetwork email routing facility that supports many kinds of mail-transfer and delivery methods, including the Simple Mail Transfer Protocol (SMTP) used for email transport over the Internet.
A descendant of t ...
- Sendmail is one of the oldest email packages
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Sieve mail filtering language - a standardised mail filtering language; also, a modern replacement for procmail from the
GNU Mailutils package
See also
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Message transfer agent
Within the Internet email system, a message transfer agent (MTA), mail transfer agent, or mail relay is software that transfers electronic mail messages from one computer to another using the Simple Mail Transfer Protocol. In some contexts, the a ...
(MTA)
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Mail retrieval agent (MRA)
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Message submission agent (MSA)
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Message user agent (MUA) a.k.a. email client
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E-mail agent (infrastructure) (MxA)
References
{{DEFAULTSORT:Mail Delivery Agent
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