A message delivery agent (MDA), or mail delivery agent, is a computer

software Software is a set of computer programs and associated documentation and data. This is in contrast to hardware, from which the system is built and which actually performs the work. At the lowest programming level, executable code consist ...

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 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 ...

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

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 procmail is an email server software component — specifically, a message delivery agent (MDA). It was one of the earliest mail filter programs. It is typically used in Unix-like mail systems, using the mbox and Maildir storage formats. pr ...

and maildrop are the most popular MDAs. The

Local Mail Transfer Protocol The Local Mail Transfer Protocol (LMTP) is an alternative to (Extended) Simple Mail Transfer Protocol for situations where the receiving side does not have a mail queue, such as a message transfer agent acting as a message delivery agent. LMTP was d ...

(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 themsel ...

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 Car ...

- 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 themsel ...

(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

alternative * fdm — modern replacement for both

and

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 The Courier Mail Server is a mail transfer agent (MTA) server that provides SMTP, IMAP, POP3, SMAP, webmail, and mailing list services with individual components. It is best known for its IMAP server component. Courier can function as an intermedi ...

, but can also be used with other mail servers *

- 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 the ...

- 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 GNU () is an extensive collection of free software (383 packages as of January 2022), which can be used as an operating system or can be used in parts with other operating systems. The use of the completed GNU tools led to the family of opera ...

package

References

{{DEFAULTSORT:Mail Delivery Agent *

Implementation

Unix

Invocation

List of MDA software for Unix-like platforms

See also

References