Internet and web designing

ASSIGNMENT

SUBMITTED BY

AMRITHA.N

162AC3389

3rd BCOM
E mail:-
Electronic mail (email or e-mail) is a method of exchanging messages ("mail")
between people using electronic devices. Invented by Ray Tomlinson, email first entered
limited use in the 1960s and by the mid-1970s had taken the form now recognized as
email. Email operates across computer networks, which today is primarily the Internet.
Some early email systems required the author and the recipient to 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 serversaccept, forward, deliver, and store messages.
Neither the users nor their computers are required to be online simultaneously; they
need to connect only briefly, typically to a mail server or a webmail interface, for as long
as it takes to send or receive messages.
Originally an ASCII text-only communications medium, Internet email was extended
by Multipurpose Internet Mail Extensions (MIME) to carry text in other character sets and
multimedia content attachments. International email, with internationalized email
addresses using UTF-8, has been standardized, but as of 2017 it has not been widely
adopted.[2]
The history of modern Internet email services reaches back to the early ARPANET, with
standards for encoding email messages published as early as 1973 (RFC 561). An email
message sent in the early 1970s looks very similar to a basic email sent today. Email
had an important role in creating the Internet,[3] and the conversion from ARPANET to
the Internet in the early 1980s produced the core of the current services.
Origin
Main article: History of email

Computer-based mail and messaging became possible with the advent of time-
sharing computers in the early 1960s, and informal methods of using shared files to pass
messages were soon expanded into the first mail systems. Most developers of early
mainframes and minicomputers developed similar, but generally incompatible, mail
applications. Over time, a complex web of gateways and routing systems linked many of
them. Many US universities were part of the ARPANET (created in the late 1960s), which
aimed at software portabilitybetween its systems. That portability helped make the Simple
Mail Transfer Protocol (SMTP) increasingly influential.
For a time in the late 1980s and early 1990s, it seemed likely that either a proprietary
commercial system or the X.400 email system, part of the Government Open Systems
Interconnection Profile (GOSIP), would predominate. However, once the final restrictions
on carrying commercial traffic over the Internet ended in 1995,[26][27] a combination of
factors made the current Internet suite of SMTP, POP3 and IMAP email protocols the
standard.
 Operation
The diagram to the right shows a typical sequence of events that takes place when
sender Alice transmits a message using a mail user agent (MUA) addressed to the email
address of the recipient.[28]

Email operation

1. The MUA formats the message in email format and uses the submission protocol, a profile of
the Simple Mail Transfer Protocol (SMTP), to send the message content to the local mail submission
agent (MSA), in this case smtp.a.org.
2. The MSA determines the destination address provided in the SMTP protocol (not from the message
header), in this case bob@b.org which is a fully qualified domain address (FQDA). The part before
the @ sign is the local part of the address, often the username of the recipient, and the part after the
@ sign is a domain name. The MSA resolves a domain name to determine the fully qualified domain
name of the mail server in the Domain Name System(DNS).
3. The DNS server for the domain b.org(ns.b.org) responds with any MX recordslisting the mail
exchange servers for that domain, in this case mx.b.org, a message transfer agent (MTA) server run
by the recipient's ISP.[29]
4. smtp.a.org sends the message to mx.b.org using SMTP. This server may need to forward the
message to other MTAs before the message reaches the final message delivery agent (MDA).
5. The MDA delivers it to the mailbox of user bob.
6. Bob's MUA picks up the message using either the Post Office Protocol(POP3) or the Internet
Message Access Protocol (IMAP).

In addition to this example, alternatives and complications exist in the email system:

▪ Alice or Bob may use a client connected to a corporate email system, such as IBM Lotus
Notes or Microsoft Exchange. These systems often have their own internal email format and their
clients typically communicate with the email server using a vendor-specific, proprietary protocol.
The server sends or receives email via the Internet through the product's Internet mail gateway
which also does any necessary reformatting. If Alice and Bob work for the same company, the entire
transaction may happen completely within a single corporate email system.
▪ Alice may not have a MUA on her computer but instead may connect to a webmail service.
▪ Alice's computer may run its own MTA, so avoiding the transfer at step 1.
▪ Bob may pick up his email in many ways, for example logging into mx.b.org and reading it directly,
or by using a webmail service.
▪ Domains usually have several mail exchange servers so that they can continue to accept mail even if
the primary is not available.
Many MTAs used to accept messages for any recipient on the Internet and do their best to
deliver them. Such MTAs are called open mail relays. This was very important in the early
days of the Internet when network connections were unreliable. [30][31] However, this
mechanism proved to be exploitable by originators of unsolicited bulk email and as a
consequence open mail relays have become rare, [32] and many MTAs do not accept
messages from open mail relays

Message format
The basic Internet email message format is now defined by RFC 5322, with encoding of
non-ASCII data and multimedia content attachments being defined in RFC
2045 through RFC 2049, collectively called Multipurpose Internet Mail
Extensions or MIME. RFC 5322 replaced the earlier RFC 2822in 2008, and in turn RFC
2822 in 2001 replaced RFC 822 – which had been the standard for Internet email for nearly
20 years. Published in 1982, RFC 822was based on the earlier RFC 733 for
the ARPANET.[33]
Internet email messages consist of two major sections, the message header and the
message body, collectively known as content. [34][35] The header is structured
into fields such as From, To, CC, Subject, Date, and other information about the email. In the
process of transporting email messages between systems, SMTP communicates delivery
parameters and information using message header fields. The body contains the message,
as unstructured text, sometimes containing a signature block at the end. The header is
separated from the body by a blank line.
Message header
Each message has exactly one header(the "header section" of the message, according to the
specification), which is structured into fields ("header fields"). Each field has a name ("field
name" or "header field name") and a value ("field body" or "header field body"). RFC
5322 specifies the precise syntax.
Informally, each line of text in the header that begins with a non-whitespaceprintable
character begins a separate field. The field name starts in the first character of the line and
ends before the separator character ":". The separator is then followed by the field value
(the "body" of the field). The value is continued onto subsequent lines if those lines have a
space or tab as their first character. Field names and, without SMTPUTF8, field bodies are
restricted to 7-bit ASCII characters. Some non-ASCII values may be represented using
MIME encoded words.
Header fields
Email header fields can be multi-line, with each line recommended to be no more than 78
characters, although the technical limit is 998 characters. [36]Header fields defined by RFC
5322 can only contain US-ASCII characters; for encoding characters in other sets, a syntax
specified in RFC 2047 can be used.[37] Recently the IETF EAI working group has defined
some standards track extensions,[38][39] replacing previous experimental extensions, to
allow UTF-8encoded Unicode characters to be used within the header. In particular, this
allows email addresses to use non-ASCII characters. Such addresses are supported by
Google and Microsoft products, and promoted by some governments. [40]
The message header must include at least the following fields: [41][42]
▪ From: The email address, and optionally the name of the author(s). In many email clients not
changeable except through changing account settings.
▪ Date: The local time and date when the message was written. Like the From: field, many email
clients fill this in automatically when sending. The recipient's client may then display the time in the
format and time zone local to them.

RFC 3864 describes registration procedures for message header fields at the IANA; it
provides for permanentand provisional field names, including also fields defined for MIME,
netnews, and HTTP, and referencing relevant RFCs. Common header fields for email
include:[43]
▪ To: The email address(es), and optionally name(s) of the message's recipient(s). Indicates primary
recipients (multiple allowed), for secondary recipients see Cc: and Bcc: below.
▪ Subject: A brief summary of the topic of the message. Certain abbreviationsare commonly used in
the subject, including "RE:" and "FW:".
▪ Cc: Carbon copy; Many email clients will mark email in one's inbox differently depending on
whether they are in the To: or Cc: list. (Bcc: Blind carbon copy; addresses are usually only specified
during SMTP delivery, and not usually listed in the message header.)
▪ Content-Type: Information about how the message is to be displayed, usually a MIME type.
▪ Precedence: commonly with values "bulk", "junk", or "list"; used to indicate that automated
"vacation" or "out of office" responses should not be returned for this mail, e.g. to prevent vacation
notices from being sent to all other subscribers of a mailing list. Sendmail uses this field to affect
prioritization of queued email, with "Precedence: special-delivery" messages delivered sooner.
With modern high-bandwidth networks, delivery priority is less of an issue than it once
was. Microsoft Exchangerespects a fine-grained automatic response suppression mechanism, the X-
Auto-Response-Suppress field.[44]
▪ Message-ID: Also an automatically generated field; used to prevent multiple delivery and for
reference in In-Reply-To: (see below).
▪ In-Reply-To: Message-ID of the message that this is a reply to. Used to link related messages
together. This field only applies for reply messages.
▪ References: Message-ID of the message that this is a reply to, and the message-id of the message the
previous reply was a reply to, etc.
▪ Reply-To: Address that should be used to reply to the message.
▪ Sender: Address of the actual sender acting on behalf of the author listed in the From: field
(secretary, list manager, etc.).
▪ Archived-At: A direct link to the archived form of an individual email message.

Note that the To: field is not necessarily related to the addresses to which the message is
delivered. The actual delivery list is supplied separately to the transport protocol, SMTP,
which may or may not originally have been extracted from the header content. The "To:"
field is similar to the addressing at the top of a conventional letter which is delivered
according to the address on the outer envelope. In the same way, the "From:" field does not
have to be the real sender of the email message. Some mail servers apply email
authenticationsystems to messages being relayed. Data pertaining to server's activity is
also part of the header, as defined below.
SMTP defines the trace information of a message, which is also saved in the header using
the following two fields:[45]
▪ Received: when an SMTP server accepts a message it inserts this trace record at the top of the
header (last to first).
▪ Return-Path: when the delivery SMTP server makes the final delivery of a message, it inserts this
field at the top of the header.

Other fields that are added on top of the header by the receiving server may be called trace
fields, in a broader sense.[46]
▪ Authentication-Results: when a server carries out authentication checks, it can save the results in
this field for consumption by downstream agents. [47]
▪ Received-SPF: stores results of SPFchecks in more detail than Authentication-Results.[48]
▪ Auto-Submitted: is used to mark automatically generated messages.[49]
▪ VBR-Info: claims VBR whitelisting[50]

Message body
Content encoding
Internet email was originally designed for 7-bit ASCII.[51] Most email software is 8-bit
clean but must assume it will communicate with 7-bit servers and mail readers.
The MIME standard introduced character set specifiers and two content transfer encodings
to enable transmission of non-ASCII data: quoted printable for mostly 7-bit content with a
few characters outside that range and base64 for arbitrary binary data.
The 8BITMIME and BINARY extensions were introduced to allow transmission of mail
without the need for these encodings, but many mail transport agents still do not support
them fully. In some countries, several encoding schemes coexist; as the result, by default,
the message in a non-Latin alphabet language appears in non-readable form (the only
exception is coincidence, when the sender and receiver use the same encoding scheme).
Therefore, for international character sets, Unicode is growing in popularity.[citation needed]
Plain text and HTML
Most modern graphic email clients allow the use of either plain text or HTML for the
message body at the option of the user. HTML email messages often include an
automatically generated plain text copy as well, for compatibility reasons. Advantages of
HTML include the ability to include in-line links and images, set apart previous messages
in block quotes, wrap naturally on any display, use emphasis such as underlines and italics,
and change fontstyles. Disadvantages include the increased size of the email, privacy
concerns about web bugs, abuse of HTML email as a vector for phishingattacks and the
spread of malicious software.[52]
Some web-based mailing listsrecommend that all posts be made in plain-text, with 72 or
80 characters per line for all the above reasons,[53][54] but also because they have a
significant number of readers using text-based email clients such as Mutt.
Some Microsoft email clients allow rich formatting using their proprietary Rich Text
Format (RTF), but this should be avoided unless the recipient is guaranteed to have a
compatible email client.[55]

Types
Web-based email
Main article: Webmail
Many email providers have a web-based email client (e.g. AOL
Mail, Gmail, Outlook.com, Hotmail 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 servers
The Post Office Protocol 3 (POP3) is a mail access protocol used by a client application to
read messages from the mail server. Received messages are often deleted from the server.
POP supports simple download-and-delete requirements for access to remote mailboxes
(termed maildrop in the POP RFC's).[60]
IMAP email servers
The Internet Message Access Protocol(IMAP) provides features to manage a mailbox from
multiple devices. 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.
CONCLUSION :-

From this assignment topic “ e mail concept” know about the topic e mail concept.

. I am thankful to our kamal sir for giving us this topic as our assignment.

Thank you.