Electronic mail, commonly known as email, allows digital messages to be exchanged between an author and recipients over computer networks like the Internet. Early email systems required both parties to be online simultaneously, but modern email uses a store-and-forward model where messages are sent to and stored on email servers until the recipient connects. An email consists of a message envelope containing sender/recipient addresses, a message header with fields like subject, and the message body. Originally only text, email has evolved to support attachments and non-ASCII character sets.

1. Introduction
Electronic mail, most commonly referred to as email
or e-mail since 1993 is a method of exchanging digital messages from an author to
one or more recipients. Modern email operates across the Internet or other
computer networks. Some early email systems required that the author and the
recipient both be online at the same time, in common with instant messaging.
Today's email systems are based on a store-and-forward model. Email servers
accept, forward, deliver, and store messages. Neither the users nor their computers
are required to be online simultaneously; they need connect only briefly, typically
to a mail server, for as long as it takes to send or receive messages. Historically,
the term electronic mail was used generically for any electronic document
transmission. For example, several writers in the early 1970s used the term to
describe fax document transmission.As a result, it is difficult to find the first
citation for the use of the term with the more specific meaning it has today.
An Internet email message consists of three components, the message envelope, the
message header, and the message body. The message header contains control
information, including, minimally, an originator's email address and one or more
recipient addresses. Usually descriptive information is also added, such as a subject
header field and a message submission date/time stamp.
Originally a text-only (ASCII) communications medium, Internet email was
extended to carry, e.g. text in other character sets, multi-media content
attachments, a process standardized in RFC 2045 through 2049. Collectively, these
RFCs have come to be called Multipurpose Internet Mail Extensions (MIME).
Subsequent RFCs have proposed standards for internationalized email addresses
using UTF-8.

2. content
An Internet email message consists of three components, the message envelope, the
message header, and the message body. The message header contains control
information, including, minimally, an originator's email address and one or more
recipient addresses. Usually descriptive information is also added, such as a subject
header field and a message submission date/time stamp.
Electronic mail predates the inception of the Internet and was in fact a crucial tool in creating
it,[5] but the history of modern, global Internet email services reaches back to the early
ARPANET. Standards for encoding email messages were proposed as early as 1973 (RFC 561).
Conversion from ARPANET to the Internet in the early 1980s produced the core of the current
services. An email sent in the early 1970s looks quite similar to a basic text message sent on the
Internet today.
Email is an information and communications technology. It uses technology to communicate a
digital message over the Internet. Users use email differently, based on how they think about it.
There are many software platforms available to send and receive. Popular email platforms
include Gmail, Hotmail, Yahoo! Mail, Outlook, and many others.[6]
Network-based email was initially exchanged on the ARPANET in extensions to the File
Transfer Protocol (FTP), but is now carried by the Simple Mail Transfer Protocol (SMTP), first
published as Internet standard 10 (RFC 821) in 1982. In the process of transporting email
messages between systems, SMTP communicates delivery parameters using a message envelope
separate from the message (header and body) itself.
Web-based email (webmail)
Many email providers have a web-based email client (e.g. AOL Mail, Gmail, Outlook.com and
Yahoo! Mail). This allows users to log into the email account by using any compatible web
browser to send and receive their email. Mail is typically not downloaded to the client, so can't
be read without a current Internet connection.
POP3 email services
POP3 is the acronym for Post Office Protocol 3. In a POP3 email account, email messages are
downloaded to the client device (i.e. a computer) and then they are deleted from the mail server
unless specific instruction to save has been given . It is difficult to save and view messages on

3. multiple devices. Also, the messages sent from the computer/one device are not copied to the
Sent Items folder on the (other) devices. The messages are deleted from the server to make room
for more incoming messages. POP supports simple download-and-delete requirements for access
to remote mailboxes (termed maildrop in the POP RFC's).[81] Although most POP clients have an
option to leave messages on the server after downloading a copy of them, most email clients
using POP3 simply connect, retrieve all messages, store them on the client device as new
messages, delete them from the server, and then disconnect.
IMAP email servers
IMAP refers to Internet Message Access Protocol. With an IMAP account, a user's account has
access to mail folders on the mail server and can use any compatible device to read and reply to
messages, as long as such a device can access the server. Small portable devices like
smartphones are increasingly used to check email while travelling, and to make brief replies,
larger devices with better keyboard access being used to reply at greater length. IMAP shows the
headers of messages, the sender and the subject and the device needs to request to download
specific messages. Usually mail is left in folders in the mail server.
MAPI email servers
Messaging Application Programming Interface (MAPI) is a messaging architecture and a
Component Object Model based API for Microsoft Windows.
How to create email account
 Go to the Google Groups website and click "Create Group." Enter a
name for the group and type in the email address you want to use,
which will end in "@googlegroups.com." Enter a description of the
group for members to view.
 2 Select "Collaborative Inbox" from the Select a Group Type drop-down
list. Choose the types of members you want to authorize to
access inbox features. Pick the basic permissions you want to apply,
such as allowing the public to view topics or allowing all group
members to post messages. Click "Create," then "OK" to manage the
inbox settings.
 3 Click the "Manage" link at the bottom of the Topics page. Click
"Invite Members" in the left pane to open an email invitation form.
Enter the email addresses of the people you want to permit to use the
inbox, type an invitation message and click "Send Invites.“
 4 Select "Roles" in the left pane and click "Roles." Choose the role for
which

4.  you want to manage settings. Add members to the role and select the
permissions you want to apply. Repeat for the remaining roles.
Depending on the roles you assign, members receive notifications via
their primary email address when anyone posts a new message.
References :
Google.com