All Abt Emal
All Abt Emal
All Abt Emal
Electronic mail (abbreviated "email" or, often, "e-mail") is a store and forward method
of composing, sending, storing, and receiving messages over electronic communication
systems. The term "e-mail" (as a noun or verb) applies both to the Internet e-mail system
based on the Simple Mail Transfer Protocol (SMTP) and to intranet systems allowing
users within one organization to e-mail each other. Often these workgroup collaboration
organizations may use the Internet protocols for internal e-mail service. E-mail is often
used to deliver bulk unwanted messages, or "spam", but filter programs exist which can
automatically delete some of these.
Contents
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• 11 External links
E-mail was quickly extended to become network e-mail, allowing users to pass messages
between different computers by at least 1966 (it is possible the SAGE system had
something similar some time before).
[edit] Flaming
Many observers bemoan the rise of flaming in written communications. Flaming occurs
when one user, usually upset at another user, sends the second user an angry and/or
antagonistic message. Flaming is assumed to be more common today because of the ease
and impersonality of e-mail communications: confrontations in person or over the phone
will often be personal-enough to encourage conversants to "hold their tongue," and
typing an unhappy message to another is far easier than seeking that other out and
confronting them directly.
[edit] Text/HTML
Both plain text and HTML are used to convey e-mail. While text is certain to be read by
all users without problems, there is a perception that HTML-based e-mail has a higher
aesthetic value. [9] Advantages of HTML include the ability to include inline links and
images, set apart previous messages in block quotes, wrap naturally on any display, use
emphasis such as underlines and italics, and change font styles. HTML e-mail messages
often include an automatically-generated plain text copy as well, for compatibility
reasons. Disadvantages include the increased size of the email, privacy concerns about
web bugs and that HTML email can be a vector for phishing attacks and the spread of
malicious software.[10]
Because in physical space traveling is difficult, time consuming and expensive, we write
down the information and the information travels instead of us.
for real time communication, all participants have to be synchronized. They need to be: at
the same time; at the same place and spend the same amount of time on the same
information.
With (e)mail, every participant can decide, when he will read it, how much time he wants
to spend on it and if he wants to interrupt reading for researching on upcoming questions.
However there are also disadvantages of using e-mail. There are many of them but the
most peculiar ones affecting corporate efficiency are as follows:
Most business professionals today spend between 20% and 50% of their working time in
communicating through e-mail[4] : reading, ordering, sorting, ‘re-contextualizing’
fragmented information and of course writing emails. And email communication is likely
to increase considerably in future due to trends of globalization, distribution of
organizations (customer closeness), outsourcing, the knowledge economy etc. E-mail
leads to a number of well known problems – a few major ones:
Despite these disadvantages, and despite the availability of other tools, e-mail based
communication is still by far the most accepted written communication media in
businesses. The main reason is the vast user base, its simplicity and the short comings of
alternative tools.
The diagram above shows a typical sequence of events that takes place when Alice
composes a message using her mail user agent (MUA). She types in, or selects from an
address book, the e-mail address of her correspondent. She hits the "send" button.
1. Her MUA formats the message in Internet e-mail format and uses the Simple Mail
Transfer Protocol (SMTP) to send the message to the local mail transfer agent
(MTA), in this case smtp.a.org, run by Alice's Internet Service Provider (ISP).
2. The MTA looks at the destination address provided in the SMTP protocol (not
from the message header), in this case bob@b.org. An Internet e-mail address is a
string of the form localpart@exampledomain.com, which is known as 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 MTA looks up this domain name in the Domain Name
System to find the mail exchange servers accepting messages for that domain.
3. The DNS server for the b.org domain, ns.b.org, responds with an MX record
listing the mail exchange servers for that domain, in this case mx.b.org, a server
run by Bob's ISP.
4. smtp.a.org sends the message to mx.b.org using SMTP, which delivers it to the
mailbox of the user bob.
5. Bob presses the "get mail" button in his MUA, which picks up the message using
the Post Office Protocol (POP3).
This sequence of events applies to the majority of e-mail users. However, there are many
alternative possibilities and complications to the e-mail system:
• Alice or Bob may use a client connected to a corporate e-mail system, such as
IBM's Lotus Notes or Microsoft's Exchange. These systems often have their own
internal e-mail format and their clients typically communicate with the e-mail
server using a vendor-specific, proprietary protocol. The server sends or receives
e-mail 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 e-mail
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 e-mail in many ways, for example using the Internet
Message Access Protocol, by 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 when the main mail exchange server is not available.
• E-mail messages are not secure if e-mail encryption is not used correctly.
It used to be the case that many MTAs would accept messages for any recipient on the
Internet and do their best to deliver them. Such MTAs are called open mail relays. This
was important in the early days of the Internet when network connections were
unreliable. If an MTA couldn't reach the destination, it could at least deliver it to a relay
that was closer to the destination. The relay would have a better chance of delivering the
message at a later time. However, this mechanism proved to be exploitable by people
sending unsolicited bulk e-mail and as a consequence very few modern MTAs are open
mail relays, and many MTAs will not accept messages from open mail relays because
such messages are very likely to be spam.
Note that the people, e-mail addresses and domain names in this explanation are fictional:
see Alice and Bob.
The format of Internet e-mail messages is defined in RFC 2822 and a series of RFCs,
RFC 2045 through RFC 2049, collectively called Multipurpose Internet Mail Extensions
(MIME). Although as of July 13, 2005 (see [11]) RFC 2822 is technically a proposed
IETF standard and the MIME RFCs are draft IETF standards, these documents are the de
facto standards for the format of Internet e-mail. Prior to the introduction of RFC 2822 in
2001 the format described by RFC 822 was the de facto standard for Internet e-mail for
nearly two decades; it is still the official IETF standard. The IETF reserved the numbers
2821 and 2822 for the updated versions of RFC 821 (SMTP) and RFC 822, honoring the
extreme importance of these two RFCs. RFC 822 was published in 1982 and based on the
earlier RFC 733.
• Header -- Structured into fields such as summary, sender, receiver, and other
information about the e-mail
• Body -- The message itself as unstructured text; sometimes containing a signature
block at the end
The message header consists of fields, usually including at least the following:
• From: The e-mail address, and optionally name, of the sender of the message
• To: The e-mail address[es], and optionally name[s], of the receiver[s] of the
message
• Subject: A brief summary of the contents of the message
• Date: The local time and date when the message was originally sent
Each header field has a name and a value. RFC 2822 specifies the precise syntax.
Informally, the field name starts in the first character of a line, followed by a ":",
followed by the value which is continued on non-null subsequent lines that have a space
or tab as their first character. Field names and values are restricted to 7-bit ASCII
characters. Non-ASCII values may be represented using MIME encoded words.
Note that the "To" field in the header is not necessarily related to the addresses to which
the message is delivered. The actual delivery list is supplied in the SMTP protocol, not
extracted from the header content. The "To" field is similar to the greeting at the top of a
conventional letter which is delivered according to the address on the outer envelope.
Also note that the "From" field does not have to be the real sender of the e-mail message.
It is very easy to fake the "From" field and let a message seem to be from any mail
address. It is possible to digitally sign e-mail, which is much harder to fake. Some
Internet service providers do not relay e-mail claiming to come from a domain not hosted
by them, but very few (if any) check to make sure that the person or even e-mail address
named in the "From" field is the one associated with the connection. Some Internet
service providers apply e-mail authentication systems to e-mail being sent through their
MTA to allow other MTAs to detect forged spam that might apparently appear to be from
them.
Other common header fields include (see RFC 4021 or RFC 2076 for more):
Many e-mail clients present "Bcc" (Blind carbon copy, recipients not visible in the "To"
field) as a header field. Different protocols are used to deal with the "Bcc" field; at times
the entire field is removed, whereas other times the field remains but the addresses
therein are removed. Addresses added as "Bcc" are only added to the SMTP delivery list,
and do not get included in the message data. There are differing impressions on the RFC
2822 Protocol pertaining to this subject.
E-mail was originally designed for 7-bit ASCII. Much e-mail software is 8-bit clean but
must assume it will be communicating 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
extension was introduced to allow transmission of mail without the need for these
encodings but many mail transport agents still don't support it fully. For international
character sets, Unicode is growing in popularity.
.eml
This is the default e-mail extension for Mozilla Thunderbird and is used by
Microsoft Outlook Express.
.emlx
Used by Apple Mail.
.msg
Used by Microsoft Office Outlook.
Mail can be stored either on the client, on the server side, or in both places. Standard
formats for mailboxes include Maildir and mbox. Several prominent e-mail clients use
their own proprietary format and require conversion software to transfer e-mail between
them.
When a message cannot be delivered, the recipient MTA must send a bounce message
back to the sender, indicating the problem.
Spamming is unsolicited commercial e-mail. Because of the very low cost of sending e-
mail, spammers can send hundreds of millions of e-mail messages each day over an
inexpensive Internet connection. Hundreds of active spammers sending this volume of
mail results in information overload for many computer users who receive tens or even
hundreds of junk messages each day.
E-mail worms use e-mail as a way of replicating themselves into vulnerable computers.
Although the first e-mail worm affected UNIX computers, the problem is most common
today on the more popular Microsoft Windows operating system.
The combination of spam and worm programs results in users receiving a constant drizzle
of junk e-mail, which reduces the usefulness of e-mail as a practical tool.
A number of anti-spam techniques mitigate the impact of spam. In the United States, U.S.
Congress has also passed a law, the Can Spam Act of 2003, attempting to regulate such e-
mail. Australia also has very strict spam laws restricting the sending of spam from an
Australian ISP (http://www.aph.gov.au/library/pubs/bd/2003-04/04bd045.pdf), but its
impact has been minimal since most spam comes from regimes that seem reluctant to
regulate the sending of spam.
There are cryptography applications that can serve as a remedy to one or more of the
above. For example, Virtual Private Networks or the Tor anonymity network can be used
to encrypt traffic from the user machine to a safer network while GPG, PGP or S/MIME
can be used for end-to-end message encryption, and SMTP STARTTLS or SMTP over
Transport Layer Security/Secure Sockets Layer can be used to encrypt communications
for a single mail hop between the SMTP client and the SMTP server.
Another risk is that e-mail passwords might be intercepted during sign-in. One may use
encrypted authentication schemes such as SASL to help prevent this.
[edit] Enhancements
• BlackBerry
• E-mail encryption
• HTML e-mail
• Internet fax
• L-mail
• Push e-mail
[edit] E-mail social issues
• E-mail spoofing
• Netiquette
• Information overload
• Internet humor
• Internet slang
• E-mail spam
• Anti-spam techniques (e-mail)
• Computer virus
• E-card
• Usenet quoting
• E-mail art
[edit] References
[edit] Notes
1. ^ "Email" is preferred by Google [1], Yahoo [2] and Apple [3]. Microsoft's use of
the hyphenated spelling, "e-mail", is an exception to the computer industry's
prevailing spelling.
2. ^ "CTSS, Compatible Time-Sharing System" (September 4, 2006), University of
South Alabama, web: USA-CTSS.
3. ^ Tom Van Vleck, "The IBM 7094 and CTSS" (September 10, 2004),
Multicians.org (Multics), web: Multicians-7094.
4. ^ Email Right to Privacy - Why Small Businesses Care. Anita Campbell (2007-
06-19).
[edit] Bibliography