In the early days of ARPANET, email is
consisted exclusively of text messages
written in English and expressed in ASCII.
For this environment , RFC 822 did the job
Nowadays, on the worldwide Internet,
this approach is no longer adequate.
The problems include sending and receiving are
1. Message in language with accents (eg:
French and German).
2. Message in nonLatin alphabets( eg: Hebrew
3. Message in language without alphebets(eg:
Chinese and Japanese)
4. Massage not containing text at all(eg: audio
MIME-Multipurpose Internet Mail
• A solution was proposed in RFC 1341 and updated in
RFC 1521.This solution called MIME is now widely used.
• The basic idea of MIME is to continue to use the RFC
822 format, but to add structure to the message body
and define encoding rules for non-ASCII messages.
• BY not deviating from 822, MIME massage can be sent
using the existing mail programs and protocols .
• All that has to be changed are the sending and receiving
programs, which users can do for themselves
• MIME defines five new message headers
MIME-Version: Identifies the MIME version
Content Description: Human-Readable string telling what is in the
Content-Id: Unique identifier
Content-Transfer-Encoding How the body is wrapped for transmission
Content-Type: Nature of the message
Text including simple formatting
Still picture in GIF format
Still picture in JPEG format
An un interpreted byte sequence
A printable document in PostScript
Rfc822 A MIME RFC 822 message
Partial Message has been split for transmission
External Body Message itself must be fetched over the net
Same message in different formats
Parts must be viewed simultaneously
Each part is a complete RFC 822message
Movie in Mpeg format
Independent parts in the specified order
• The message transfer system is
concerned with relaying ,messages from
originator to the recipient.
• Establish a transport connection from the
source machine to the destination
• There are situations in which this does not
• To overcome this we can do is ….
SMTP-Simple Mail Transfer
• Within the Internet email is delivered by having
the source machine establish a TCP connection
to port 25 of the destination machine
• Listening to this port is an email daemon that
speaks SMTP .
• SMTP is a simple ASCII protocol.
• If the server is willing to accept mail, the client
announces whom the email is coming from and
whom it is going to.
• Email using SMTP works best when both
the sender and the receiver are on the
Internet and can support TCP connection
between sender and receiver. However,
many machines that are not on the
Internet still want to send and receive
email from Internet sites.
• A simple protocol used for fetching email from a
remote mailbox is POP3(Post Office Protocol)
which is defined in RFC 1225.
• A more sophisticated delivery protocol is
IMAP(Interactive Mail Access Protocol) which is
defined in RFC 1064.
• The third delivery protocol is DMSP(Distributed
Mail System Protocol), which is part of the
PCMAIL system and described in RFC 1056.
• Independent of whether email is delivered directly to the
workstations or to a remote server, many systems
provide hooks for additional processing of incoming
• An especially valuable tool for many email users is the
ability to set up filters.
• These are rules that are checked when email comes in
or when the user agent is started. Each rule specifies a
condition and an action.
• Another delivery feature often provided is
the ability to forward incoming email to a
different address. This address can even
be a computer operated by a commercial
• Ability to install a vacation daemon.
• When an email message is sent between
two distant sites, it will generally transit
dozens of machines on the way.Any of
these can read and record the message
for future use.
• Widely used secure email systems are.