An email client also mail user agent or email reader is a frontend computer
program used to manage email. Sometimes, the term email client is also
used to refer to any agent acting as a client toward an email server,
independently of it being a real mua, a relaying server, or a human typing
directly on a telnet terminal.
In addition, a web application providing the relevant functionality is
sometimes considered an email client. Electronic mailing lists are usually
fully or partially automated through the use of special mailing list software
and a reflector address that are set up on a server capable of receiving
email. Incoming messages sent to the reflector address are processed by the
software, and, depending on their content, are acted upon internally in the
case of messages containing commands directed at the software itself or
are distributed to all email addresses subscribed to the mailing list.
Depending on the software, additional addresses may be set up for the
purpose of sending commands. Many electronic mailing list servers
have a special email address in which subscribers or those that want to be
subscribers can send commands to the server to perform such tasks as
subscribing and unsubscribing, temporarily halting the sending of messages
to them, or changing available preferences.
The common format for sending these commands is to send an email that
contains simply the command followed by the name of the electronic
mailing list the command pertains to. Examples subscribe anylist or
subscribe anylist John Doe. Some list servers also allow people to
subscribe, unsubscribe, change preferences, etc. via a website.
