E-mail-I

CS-3505

Wb_e-mail-I.ppt

Email

The most useful feature of the internet Lots of different email programs, but most

of them can talk to each other.

How email works

Two types of programs interact: delivery mail agent & user mail agent

What you see on your desktop is the mail user agent, eg, Eudora, Outlook, Netscape Message center

Your user mail agent sends mail to the delivery mail agent, eg, Microsoft Exchange, sendmail which sees it gets to the destination

Examples of mail agents

Eudora--Windows, Mac, very popular, free (www.eudora.com)

Netscape message center--already present in Netscape download, free (home.netscape.com)

Outlook Express--From MS. Free with Internet Explorer 4.0

Command line stuff on Unix (elm, pine)

Delivery Agents & User Agents

Your PCrunning mail user agent Outlook Express

NPS Mail Server running delivery agent

Mail server

User PC runningmail user agentEudora,Outlook,etc

Running Mail Access Server

running Mail delivery agent

SMTP

SMTP

POP or IMAP

mailbox

Delivering Mail

You compose a message on your PC, then hit the ‘send’ button

The message is sent to the mail delivery agent at NPS. You must have an account that the mail delivery agent recognizes

The MDA saves the message and attempts to deliver it to the destination MDA. The destination MDA may be down, so it can’t be delivered immediately

Eventually it gets delivered to the destination server MDA, where it is saved

When the recipient wants to read his mail, he downloads it from the Mail Sever MDA to his local PC

E-MAIL Addresses

local_mailbox@ServerDomainName Example

– Cs3505prof@hotmail.com Server name assigned by the internet naming

system implemented by DNS. Local Mailbox name Assigned by local mail

administrator as an account Aliases “address book” “nikname” local mailer

translation from a short name to the full address

MAIL PROTOCOLS

SMTP- Simple Mail Transfer Protocol– See: RFC 821 and RFC 822– http://raddist.rad.com/networks/1998/smtp/

smtp.htm– MIME MultiPurpose Internet Mail Extension

POP , POP3 Post Office Protocol IMAP – Internet Mail Access Protocol Outlook express uses POP3 or IMAP

SMTP Example

>>> HELO sun.tuc.noao.edu

250 noao.edu Hello sun.tuc.noao.edu., pleased to meet you 

>>> MAIL From:rstevens@sun.tuc.noao.edu

250 <rstevens@sun.tuc.noao.edu>... Sender ok 

>>> RCPT To:rstevens@noao.edu

250 <rstevens@noao.edu>... Recipient ok 

>>> DATA354 Enter mail, end with “.” on a line by itself 

>>> .

250 Mail accepted 

>>> QUIT221 noao.edu delivering mail 

SENDING

SMTP

RECEIVING

SMTP

Using email

Send something– Netscape– Eudora– Outlook Express

Netscape

Outlook

Email courtesy

Don’t spam the world Use plain ASCII text if possible There aren’t any physical cues with the text,

so it’s easy to be misunderstood. Email is more informal than a memo but more permanent than a conversation. (See Microsoft trial)

Be concise, and to the point

Email Privacy

Email is not very private. – Stays on MDA servers, where it can be

compromised– No expectation of privacy if you’re using your

employer’s system for email. They can, legally, read your email

– Password vulnerability– Hard disk compromise

Sending Attachments

Sending a file can be tricky. – Cut & paste from word processing document

loses formatting – Mail client can’t always interpret format

MIME format mail lets you send attachments in any format--the files are passed through exactly as is to the other side

Sending Attachments

Eudora--click on the paperclip button Outlook Express: New mail->insert->file Netscape: New message->attach

On the receiving side the attachment may be saved in a special directory after being received. In Outlook it is stored in the Personal Folder or Mailbox file

Attachments

Most modern mailers support MIME these days

MIME is a standard--even mail clients from different vendors can understand it

Can be dangerous--since anything can be sent, programs can be sent to. Also Word Macro viruses.

MIME

MultiPurpose Internat Mail Extensions Purpose – Converts non ASCII to 7 bit

ASCII for transmission over SMTP

SMTP

MIMEMIME

SMTP

sender receiver

7-bit NVT ASCII

Non ASCII codes

Web-based Email

What is it?– Web companies providing free email service in

exchange for eyeballs

Why would you use it?– Distinct from your company’s email system– Easy to check on the road--mail servers not always

visible from outside the system– More reliable than company mail

• Yahoo is unlikely to go down or lose network access

Who Provides it?

Yahoo.com hotmail.com deja.com whowhere.com

Delivery Agents & Web Browser

Your PCrunning mail user agent

NPS Mail Server running delivery agent

Hotmail.com

User PC runningHTML Client

Running HTML Server

running Mail delivery agent

SMTP

SMTP

HTTP

Mail database

How does it work?

Almost the same as the earlier diagram, but the download from the receiving MDA is done via a web browser instead of a dedicated program like Eudora or MS Express.

Highlights

User mail agents interact with mail delivery agents to send mail

You can use many different email programs and still communicate

You can use web-based email Email privacy is not a given

Using Hotmail.com

Browser go to www.hotmail.com

Using Hotmail

Inbox , Compose, Address book