A mail retrieval agent (MRA) is a
computer
A computer is a machine that can be programmed to Execution (computing), carry out sequences of arithmetic or logical operations (computation) automatically. Modern digital electronic computers can perform generic sets of operations known as C ...
application that retrieves or fetches
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 ...
from a remote mail server and works with a
mail delivery agent 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 mailbox., ''Internet Mail Architecture'', D. Crocker (July 2009) It is also call ...
to deliver mail to a local or remote
email mailbox A mailboxISO/IEC 2382:2015 (also electronic mailbox, email box, email mailbox, e-mailbox) is the destination to which electronic mail messages are delivered.
It is the equivalent of a letter box in the postal system.
Definitions
A mailbox is identi ...
. MRAs may be external applications by themselves or be built into bigger applications like a
mail user agent
The mail or post is a system for physically transporting postcards, letters, and parcels. A postal service can be private or public, though many governments place restrictions on private systems. Since the mid-19th century, national postal syst ...
. Significant examples of standalone MRAs include
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
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 ...
.
MuttWiki: MailConcept
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The concept of an MRA is not standardized in email architecture. Although they operate like mail transfer agent
The mail or post is a system for physically transporting postcards, letters, and parcels. A postal service can be private or public, though many governments place restrictions on private systems. Since the mid-19th century, national postal syst ...
s, MRAs are technically clients when they retrieve and submit messages.
Delivery mechanisms
The mail retrieval agent may support delivery of retrieved mail via the following mechanisms:
* Via a mail transport agent (Listening for SMTP
The Simple Mail Transfer Protocol (SMTP) is an Internet standard communication protocol for electronic mail transmission. Mail servers and other message transfer agents use SMTP to send and receive mail messages. User-level email clients typical ...
transfers on port 25)
* Via a mail delivery agent
* Direct delivery to an mbox
Mbox is a generic term for a family of related file formats used for holding collections of email messages. It was first implemented in Research Unix, Fifth Edition Unix.
All messages in an mbox mailbox are concatenated and stored as plain text ...
formatted mailbox
* Direct delivery to a maildir
The Maildir e-mail format is a common way of storing email messages in which each message is stored in a separate file with a unique name, and each mail folder is a file system directory. The local file system handles file locking as messages are ...
directory
* Output to standard output
In computer programming, standard streams are interconnected input and output communication channels between a computer program and its environment when it begins execution. The three input/output (I/O) connections are called standard input (stdin ...
Multiple mailbox support
The mail retriever agent may support retrieval of mail from multiple mailboxes simultaneously. This enables a mailserver to have a centrally configured mail retriever agent that runs against a dedicated mail system account, and collects the mail for all users in a single invocation (rather than using cron
The cron command-line utility is a job scheduler on Unix-like operating systems. Users who set up and maintain software environments use cron to schedule jobs (commands or shell scripts), also known as cron jobs, to run periodically at fixed ti ...
to run a mail retriever agent against all the mail recipients).
See also
* Email agent (infrastructure) (MxA)
References
Bibliography
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Email agents
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