A mail delivery agent
or message 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
fdm (e-mail utility) - A combined mail retrieval agent and mail delivery agent - for complex mail sorting, the man page refers users to maildrop
fetchmail - Primarily a Mail retrieval agent (MRA)
getmail - simpler, more secure, modern fetchmail alternative
mpop - Faster, more modern fetchmail alternative
mailagent - an MDA with manual config for many parameters such as timezone; seems to have a Debian package at least.
maildrop or courier-maildrop (same program?) - traditional procmail replacement
postdrop or postfix-maildrop (same program?) - A mail delivery agent for use with the postfix mail transport agent; see also the Postfix daemons smtp, local, virtual (?).
sieve - a more modern replacement for procmail from the GNU Mailutils package
Obsolete MDA software for Unix-like platforms
bin/mail, the MDA part of Sendmail - Sendmail is one of the oldest email packages
DBMail - MDA written in C by Eelco van Beek and Roel Rozendaal. Provides IMAP and POP3 daemons that use a MySQL or PostgreSQL mail store. Old? That URL refers to a web service today it seems.
dystill - A filtering MySQL database driven mail delivery agent - obsolete or old, no Debian package.
procmail - obsolete since it is unmaintained; old, but still used
Message transfer agent (MTA)
Mail retrieval agent (MRA)
Mail submission agent (MSA)
Mail user agent (MUA) a.k.a. email client
E-mail agent (infrastructure) (MxA)