Diploma in Management and Public Administration
Data Networks
E-mail: concepts
Department of Computer Languages and Systems.
Professor: Manuel Fernández Barcell.
Data Networks
E-mail: concepts
General Index
1 EMAIL …………………… ………………………………………….. …………. 3
1.1 PROTOCOLS AND ADDRESSES ……………………….. ………………………………………….. …….. 4
1.2 SCHEDULE OF THE MAIL SYSTEM ………………………….. ………………………………………. 4
1.3 SENDING A MESSAGE TO SOMEONE …………………………………….. ………………………………… 5
1.4 STRUCTURE OF A MESSAGE … ………………………………………….. …………………. ………… 5
1.5 MAILBOXES AND FOLDERS ………………………… ………………………………………….. ……………. 6
1.6 OTHER CHARACTERISTICS ……………………… ………………………………………….. …………… 6
2 MIME (1) AND THE SPECIAL CHARACTERS (ACCENTS AND EÑES) ………… 7
2.1 MIME …………………………………………. ………………………………………….. …………… 9
2.2 UUENCODE / UUDECODE ……………………… ………………………………………….. ..10
3 SMAILER …………………………………… ………………………………………….. ………………….. 10
4 PGP ………………… ………………………………………….. ………………………………………….. ….. 12
4.1 INTRODUCTION ………………………………… ………………………………………….. ……. …….. 12
4.2 SECURE ELECTRONIC MAIL AND PGP ………………………….. ………………………………… 13
4.3 DIGITAL SIGNATURES …. ………………………………………….. ……………………………………… 14
4.4 PGP …………………………………………. ………………………………………….. ……………… 14
4.4.1 Installation and operation of PGP ……………….. ………………………………….. 14
4.5 PGP 5.5I FAQ IN SPANISH SEE. 1.1 (JULY 98) ……………………………………… ..17
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Data networks
E-mail: concepts
E-mail
1 E-mail
The idea of e-mail is easy to understand because it is analogous to postal mail
traditional. To send a letter to another person, we have to write the letter, write
the address of the recipient, and deposit it in a mailbox.
The email is similar. We have to write the message, but instead of
with pencil and paper, we use a computer, and an email program. For
send the letter we use the global computer networks instead of the service of
emails.
The email is a utility that allows us to exchange messages
between computer users (local or remote) ) although the users are not connected
at that time.
The electronic mail system stores it until the recipient of the message
decides to read it.
Its main virtue is that it allows us to send messages to any part of the
world. For this, it is enough for the destination user to have an account on a machine that
is on the Internet. Normally the user is notified that mail has arrived when he enters
the computer on which he has defined his mailbox. It is usually a multi-user machine
with which it connects, and informs you of the messages that arrived. Methodologies
more modern, even allow mail to be treated directly from a
personal computer in your office. Having a mailbox in which to receive the mail is neither
more nor less than owning an account on an Internet machine
(usually a Unix machine). If you have one of these accounts, then
you can possibly send and receive mail anywhere in the world. It differs from
traditional mail in several things:
• It is not necessary to pay for each message we send.
• It is much faster.
• The document that is sent is electronic and not paper.
• The transmission media are electronic, usually through the means
that make up the Internet.
simultaneous.
• The same copy of the message is easy to distribute to several recipients
• The The sender and the receiver must not agree in an instant, so that the
issuer can send their message and the receiver can receive it. If not that it is understood that
the sender sends his message and that when it arrives, at some point the receiver
enters his machine and it notifies him that a message has arrived from such a person.
Sometimes this is an advantage in that in long communications
distance there may be time differences that make it difficult for the sender and
the receiver to be working or even awake at the same time.
E-mail is not a single Internet application, or protocols
TCP / IP, but it exists in many other networks, sometimes using the same
communications infrastructure. Thus, on occasion, it is necessary to send electronic mail
to a user who is not on the Internet, for which there are specific machines
called gateways or mail gateways that allow mail to be sent between
different systems. There are known gateways, for Bitnet, Compuserve, Fidonet,
UUCP, etc. networks
3
Data networks
E-mail: concepts
1.1 Protocols and addresses
As we have already mentioned there are various computer networks using different
mail protocols. Each protocol uses its own address system.
There are gateways that interconnect networks and translate addresses of heterogeneous
formats.
INTERNET uses the SMTP protocol (Simple Mail Transfer Protocol – Protocol
for simple mail transfer) ). Describes the format of electronic mail messages
and how they should be handled for delivery. The format of
address is called RFC-822.
name @ domain
1.2 Scheme of the mail system
The email system has several layers or agents, each of
being responsible for them of certain missions to ensure the correct functioning of the system. The three
"agents" there are are the following:
USER AGENT (AU)
TRANSPORTATION AGENT (AT)
DISTRIBUTION AND DELIVERY AGENT (AD)
Examples of each of these agents are the following:
/ bin / mail
Mush
MH The
m
RMAI
L
Zmail
mailtool
AU
/ bin / mail
local
/ mail11dv
DECnet
/ usr / lib / sendmail
/ usr / lib / uucp / uux
sedmail
UUCP
SMTP (Internet)
Let's see the functions of each one of the mentioned agents.
User agent
It is the application that the user uses for the handling of the electronic mail. Interact
directly with the user and with the Internet mail system. It allows sending
new messages, reading them, deleting them, receiving mail, managing their mailboxes and folders and
many more things.
AT
AD.
There are several user agents, each with her CARACTERISTICS. In the same
system several may coexist. Each one will have to decide which one he wants his
favorite user agent to be and learn its use. It is not necessary or useful to learn all.
The following relationship comments one of the most popular.
Comparison between different email users:
/ bin / mail
•
• Mail, mailx
•
elm
Mail.
• MH
Very simple and poor; old.
It is in all systems. Quick. Line interface.
Screen menu, with help. Very easy. Slower than
Many independent commands for each function.
Well if you have a good memory and you get a lot of mail.
• Rmail
•
• Eudora, Pegasus, MS mail
For friends of GNU Emacs.
Use menus, very simple to use.
Client for Windows
pine
We are not going to give a course of each of these programs. Yes, we are going to comment
which are the usual operations when we work with electronic mail
putting some example with Ximian Evolution.
4
Data networks
Email: concepts
No matter which agent we choose, the procedure is the same in everyone. What
first and most important to know is how to get "help". Once achieved,
simply read it.
Learning how to use email is practically learning to manage our
preferred mail agent. We will see the most frequent operations with email.
1.3 Send a message to someone
Before sending a message, we will see some necessary concepts. The first thing
that we need to know about the person to whom you want to send an electronic message is
your email address. If we have not done it, now we will tell you which one is yours.
The electronic addresses have the format of domains.
The second thing we have to do is build the electronic message that
we want to send. Let's see the structure of a message.
1.4 Structure of a message
An electronic message has the following parts:
• A header.
• The text.
• The signature. [19659002] The header
The header consists of a series of fields. Not all the fields that we are going to comment
have to be present. The most frequent are the following:
• From the real address of the sender.
• Received: paths through which the message has come.
• Date: date and time of sending.
• From: Address to which it can be replicated.
Subject: subject, brief summary of the message.
•
• To: message recipient.
• Cc: Carbon copy; a copy of the message will be sent to all recipients
that appear in this section.
• Bcc: Blind carbon copy; copies are sent but the receiver, in the message, no
appears this field. Therefore, the original recipient of the message (to:) will not know
that a copy of the message has been sent to other people
the message.
• Attachements: We indicate the names of the files that we want to include in
• Message-id: N1 identification of m
.
from Nettech Post http://bit.ly/2BTGT3C
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