A
message delivery agent (
MDA), 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 (
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 Email 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
-
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
See also
-
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)
