How Does Email Work?

Network traffic like your email message is broken up into pieces called "packets "or "datagrams," which have addressing information attached.  They are moved through a LAN or the Internet to your recipient by network devices such as routers, bridges and gateways.

SMTP

(Simple Mail Transfer Protocol) is used for moving mail on the Internet. It is limited to the standard 127 key US ASCII character set.

MIME

Multipurpose Internet Mail Extensions. Provides method for applications to determine what type of data is in mail and provides standard encoding method for sending data, including attachments. MIME allows you to use other character sets by using "Quoted-Printable." Quoted-Printable takes non-US-ASCII characters and "translates" them into ASCII for the trip accross the Internet. Your recipient's MIME compatible mail reader translates the message back into readable characters. MIME allows readers to communicate data types with the "Content-Type" label.

Take a look at the following message.  It contains ñ, which is part of the ISO-8859-1 Character Set.

Next look at a US-ASCII message.  Notice the "Content-Type."  Eudora negotiates it automatically.

This should also work with Japanese (for example) character sets.  Both sender and recipient would need CLIENT software that would deal with the characters.  MIME with the conversion for TRANSPORT accross the Internet.  Remember, SMTP is US-ASCII only.

What route does it travel?

This is a traceroute from the Library Web Server to pop-dno1.cis.yale.edu, where library staff get their email

traceroute to aeternitas.cis.yale.edu (130.132.143.31), 30 hops max, 40 byte packets
1 pride.net.yale.edu (130.132.21.1) 3 ms 2 ms 2 ms
2 sloth.net.yale.edu (130.132.1.17) 1 ms 1 ms 1 ms
3 aeternitas.cis.yale.edu (130.132.143.31) 2 ms * 7 ms

This is a traceroute to mail.navix.net in Lincoln, NE, the server that my mother uses for email

traceroute to mail.navix.net (207.91.5.4), 30 hops max, 40 byte packets
1 pride.net.yale.edu (130.132.21.1) 3 ms 2 ms 2 ms
2 bifrost.net.yale.edu (130.132.1.100) 3 ms 4 ms 2 ms
3 border7-serial4-4.WestOrange.mci.net (204.70.71.109) 31 ms 31 ms 53 ms
4 core2-fddi-0.WestOrange.mci.net (204.70.64.49) 48 ms 45 ms 33 ms
5 somerouter.sprintlink.net (206.157.77.106) 46 ms 169 ms 212 ms
6 somerouter.sprintlink.net (206.157.77.106) 34 ms 41 ms 38 ms
7 sl-pen-18-P4/0/0-155M.sprintlink.net (144.232.0.73) 62 ms 48 ms 42 ms
8 sl-pen-20-P4/0/0-155M.sprintlink.net (144.232.0.69) 58 ms 48 ms 35 ms
9 sl-pen-17-P4/0/0-155M.sprintlink.net (144.232.0.65) 50 ms 35 ms 37 ms
10 sl-chi-2-H6/1/0-T3.sprintlink.net (144.228.10.38) 71 ms 117 ms 53 ms
11 sl-chi-16-F0/0.sprintlink.net (144.228.50.16) 58 ms 57 ms 89 ms
12 sl-lincoln-2-H-T3.sprintlink.net (144.228.156.34) 66 ms 81 ms 73 ms
13 iac6.navix.net (207.91.5.4) 63 ms 68 ms 72 ms

How does it work in the Library?

We use UNIX email at Yale.
There are email servers available for all platforms though, and you could run one on your desktop computer if you wanted to.
Most library staff have POP-only accounts.  These accounts require a POP "client" like Eudora or Netscape to receive mail.  The client attaches to the server and downloads the messages to the local computer.  

These accounts have no access to a UNIX "shell," which brings us to the other type of email in use in the library.  This more traditional email is read through a telnet session:

Most people at Yale use Pine (shown above), the "supported" reader, but there others available here, including plain-old Unix Mail, Elm, Emacs, and readers for X-Windows.  Of course, users with "Full-Service Pantheon" accounts can still use Eudora.

How Does Email Addressing Work?

John Coleman <jcoleman@pantheon.cis.yale.edu> is an email address.

jcoleman is the "who" that I am sending mail to. The computer ignores what's outside of the angle brackets <>.

To the right of the @ sign is the "where." The first level domain in my address is "edu." Other first level domains include com, mil, org, net, gov. Except in the USA, first level domains are usually a 2 letter country code. The second level domain is "yale," etc...moving right to left, general to specific.

How do you find someone's email address?

• The easiest way is to ask.
  
• If they work for a university or large company, try the institution's home page.
  
• You can also try a directory like Yahoo People Search, but be aware that these directories are frequently out-of-date.

Revised 3/18/97
john.coleman@yale.edu