Mail delivery agent

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A mail delivery agent or message delivery agent (MDA) is a computer software component that is responsible for the delivery of e-mail messages to a local recipient's mailbox.[1] 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).


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.


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.[citation needed]


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[edit]

  • 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
  • maildrop or courier-maildrop (same program?) - traditional procmail replacement
  • procmail - obsolete since it is unmaintained; old, but still used
  • bin/mail, the MDA part of Sendmail - Sendmail is one of the oldest email packages
  • sieve - a more modern replacement for procmail from the GNU Mailutils package

See also[edit]


  1. ^ RFC 5598, Internet Mail Architecture, D. Crocker (July 2009)