Mail Info
Overview
You can divide the mail system into servers, clients, and the mail itself.
Servers are the programs that exchange mail across the internet,
and store mail until a user reads it. They talk to other servers
to get mail onto those systems, and to local clients to let users access
their mail.
Clients are the programs that users run to read and write mail,
they talk to servers to handle the actual transfer. Clients should
have a nice user interface. Eudora and Messenger Mailbox are two
example clients.
Mail is the actual data to be transfered. This can enclude
complex types like pictures and sounds or compound items like entire message
boxes.
Types of Mail Server Protocols
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SMTP
Simple Mail Transfer Protocol
This is the standard internet mail protocol. It is used betwen
hosts to exchange mail. In particular, it is the protocol used by
the 'fake mail from God' handout that I gave. SMTP can
only handle normal text. Anything extra (pictures, binaries, etc)
must be encoded as normal text and then decoded by the mail client.
SMTP does not exchange mail between clients and servers, just between
servers!
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POP
Post Office Protocol
This is the older protocol between clients and servers. Once
a client has downloaded a mail, it cannot be re-uploaded. Therefore,
POP is not good for people who want to keep mail handy and yet run
on multiple clients.
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IMAP
Internet Messaging Protocol
This is the new protocol between clients and servers. It lets
clients both download and save messages on the server. Therefore,
multiple clients can share the same mailboxes.
Types of Mail Clients
There are a zillion of these. The most famous ones are Eudora and
Lotus Notes. The good ones have these features
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Can speak all the protocols.
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Great user interface
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Can save, sort and search mail
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Can handle all the types of Mail.
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Have an address book.
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Autorespond
Web Based Mail
People these days are putting up websites offering free email. Basically,
they are making a web interface to some traditional mail protocol.
Their servers speak SMTP, and the clients speak http into your web client.
They make money from advertising.
This is a cheap way to get an anonymous email account. The site
www.mail.com is one.
Types of Mail
There are several different types of mail
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TEXT
Plain boring text with no color or formatting. Takes up little
space. Easy to read. Generally a weak format, however.
Very very common.
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HTML
They just send you the HTML page. This gives you nice fonts,
columns, JavaScript, and such. But you can only send one file per
mail message, therefore nothing that depends on multiple files can be sent.
For example, no pictures or frames.
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MIME -- Multipurpose Internet Mail Extensions
This is a way of sending multiple files per email message. Each
file is encoded into normal text, and is seperated from the next file by
a text divider. Each file is encoded with a type, such as 'image/gif'
or 'text/html'. Any time of file can be sent. For example,
if you attach a spreadsheet to a message, it's MIME encoded. However,
only people with a compatable spreadsheet program can read it.
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Combination
Often I get mail that is MIME encoded. The mail has two files,
a raw text file and an HTML file. My weak client shows me the text.
Other people with good viewers get to see the HTML page (which looks nicer).
Virus's in Mail
Often people will tell you 'Don' t open any mail with the subject 'XXXYYYZZZ'.
It will reformat your hard drive. Back when all mail was text, this
was impossible. Now it can happen. Here's how.
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Make a file with some application that allows you to attach an autorun
macro to a file. Add a 'bad' macro' that does some evil deed.
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Send the file to a victum.
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When the victum displays the file, the macro will run and the 'bad' thing
will happen.
You are safe if ANY of these is true.
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The message is in normal text
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You don't view the attachment, and your email client doesn't view it for
you.
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The application doens't support autorun macros.
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You trust the sender.
Mail Lists and Listservs
Listservs are programs that read and write mail, and manage lists of users.
In particular, any mail sent to them gets sent to everyone on this list.
Normally, everyone on the list will want to discuss some common topic,
for example The Linux Kernel. Anyone with a question or comment writes
to 'linux-kernel-digest@vger.rutgers.edu', and everyone gets a copy.
Listservs can filter out bad mail by only letting approved writers write
to it. They can archive material for later searching. Most
lists have a web page that tells the purpose of the list and allows searching
over the archive.
A good place to search for a mailing list for you is http://dir.yahoo.com/Computers_and_Internet/Internet/Mailing_Lists/.
Encrypting Mail
Yes, you can encrypt your mail. And anybody with both a compatatble
decription program and your password can decript it. The standard
common program is PGP. See www.pgp.com for much more.