A message delivery agent (MDA), or mail delivery agent, is a computer
software
Software is a set of computer programs and associated software documentation, documentation and data (computing), data. This is in contrast to Computer hardware, hardware, from which the system is built and which actually performs the work.
...
component that is responsible for the delivery of
e-mail
Electronic mail (email or e-mail) is a method of exchanging messages ("mail") between people using electronic devices. Email was thus conceived as the electronic (digital) version of, or counterpart to, mail, at a time when "mail" meant ...
messages to a local recipient's
mailbox.
[, ''Internet Mail Architecture'', D. Crocker (July 2009)] 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).
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), or mail transfer agent, or mail relay is software that transfers electronic mail messages from one computer to another using SMTP. The terms mail server, mail exchanger, and MX host ...
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 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 Unix-li ...
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), or mail transfer agent, or mail relay is software that transfers electronic mail messages from one computer to another using SMTP. The terms mail server, mail exchanger, and MX host ...
, or a
mail retrieval agent
A mail retrieval agent (MRA) is a computer application that retrieves or fetches e-mail from a remote mail server and works with a mail delivery agent to deliver mail to a local or remote email mailbox. MRAs may be external applications by them ...
.
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
Fetchmail is an open-source software utility for POSIX-compliant operating systems which is used to retrieve e-mail from a remote POP3, IMAP, or ODMR mail server to the user's local system. It was developed from thpopclientprogram, written by Ca ...
- Primarily a
Mail retrieval agent
A mail retrieval agent (MRA) is a computer application that retrieves or fetches e-mail from a remote mail server and works with a mail delivery agent to deliver mail to a local or remote email mailbox. MRAs may be external applications by them ...
(MRA)
*
getmail
getmail is a simple mail retrieval agent intended as a replacement for fetchmail, implemented in Python. It can retrieve mail from POP3, IMAP4, and ''Standard Dial-up POP3 Service'' servers, with or without SSL. It supports simple and domain ...
- simpler, more secure, modern
fetchmail
Fetchmail is an open-source software utility for POSIX-compliant operating systems which is used to retrieve e-mail from a remote POP3, IMAP, or ODMR mail server to the user's local system. It was developed from thpopclientprogram, written by Ca ...
alternative
*
fdm — modern replacement for both
fetchmail
Fetchmail is an open-source software utility for POSIX-compliant operating systems which is used to retrieve e-mail from a remote POP3, IMAP, or ODMR mail server to the user's local system. It was developed from thpopclientprogram, written by Ca ...
and
procmail from the author of
tmux
tmux is an open-source terminal multiplexer for Unix-like operating systems. It allows multiple terminal sessions to be accessed simultaneously in a single window. It is useful for running more than one command-line program at the same time. ...
*
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
See also
*
Message transfer agent
Within the Internet email system, a message transfer agent (MTA), or mail transfer agent, or mail relay is software that transfers electronic mail messages from one computer to another using SMTP. The terms mail server, mail exchanger, and MX host ...
(MTA)
*
Mail retrieval agent
A mail retrieval agent (MRA) is a computer application that retrieves or fetches e-mail from a remote mail server and works with a mail delivery agent to deliver mail to a local or remote email mailbox. MRAs may be external applications by them ...
(MRA)
*
Message submission agent (MSA)
*
Message user agent (MUA) a.k.a. email client
*
E-mail agent (infrastructure) (MxA)
References
{{DEFAULTSORT:Mail Delivery Agent
*