How Email Works

[shivashankar]

Email is based around the use of electronic mailboxes. When an email is
sent, the message is routed from server to server, all the way to the
recipient's email server. More precisely, the message is sent to the mail
server tasked with transporting emails (called the MTA, for Mail Transport
Agent) to the recipient's MTA. On the Internet, MTAs communicate with one
another using the protocol SMTP, and so are logically called SMTP servers
(or sometimes outgoing mail servers).

The recipient's MTA then delivers the email to the incoming mail server
(called the MDA, for Mail Delivery Agent), which stores the email as it
waits for the user to accept it. There are two main protocols used for
retrieving email on an MDA:

* POP3 (Post Office Protocol), the older of the two, which is used for
retrieving email and, in certain cases, leaving a copy of it on the
server.
* IMAP (Internet Message Access Protocol), which is used for
coordinating the status of emails (read, deleted, moved) across
multiple email clients. With IMAP, a copy of every message is saved on
the server, so that this synchronisation task can be completed.

For this reason, incoming mail servers are called POP servers or IMAP
servers, depending on which protocol is used.

To use a real-world analogy, MTAs act as the post office (the sorting area
and mail carrier, which handle message transportation), while MDAs act as
mailboxes, which store messages (as much as their volume will allow) until
the recipients check the box. This means that it is not necessary for
recipients to be connected in order for them to be sent email.

To keep everyone from checking other users' emails, MDA is protected by a
user name called a login and by a password.

Retrieving mail is done using a software program called an MUA (Mail User
Agent).

When the MUA is a program installed on the user's system, it is called an
email client (such as Mozilla Thunderbird, Microsoft Outlook, Eudora Mail,
Incredimail or Lotus Notes).

When it is a web interface used for interacting with the incoming mail
server, it is called webmail.

Regards,

Shiva Shankar N.