E-mail-I

1. E-mail-I CS-3505 Wb_e-mail-I.ppt

2. Email • The most useful feature of the internet • Lots of different email programs, but most of them can talk to each other.

3. 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

4. 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)

5. Delivery Agents & User Agents running Mail delivery agent SMTP NPS Mail Server running delivery agent Mail server Running Mail Access Server mailbox SMTP POP or IMAP Your PC running mail user agent Outlook Express User PC running mail user agent Eudora,Outlook,etc

6. 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

7. 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

8. 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

9. SMTP Example SENDING SMTP RECEIVING SMTP >>> 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 

10. Using email • Send something • Netscape • Eudora • Outlook Express

11. Netscape Outlook

12. 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

13. 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

14. 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

15. 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

16. 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.

17. MIME • MultiPurpose Internat Mail Extensions • Purpose – Converts non ASCII to 7 bit ASCII for transmission over SMTP SMTP SMTP 7-bit NVT ASCII MIME MIME Non ASCII codes sender receiver

18. 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

19. Who Provides it? • Yahoo.com • hotmail.com • deja.com • whowhere.com

20. Delivery Agents & Web Browser running Mail delivery agent SMTP NPS Mail Server running delivery agent Hotmail.com Running HTML Server Mail database SMTP HTTP Your PC running mail user agent User PC running HTML Client

21. 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.

22. 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

23. Using Hotmail.com • Browser go to www.hotmail.com

24. Using Hotmail • Inbox , Compose, Address book