CS 497C – Introduction to UNIX Lecture 38: - Electronic Mail

1. CS 497C – Introduction to UNIXLecture 38: - Electronic Mail Chin-Chih Changchang@cs.twsu.edu

2. Email Basics • Email is a inexpensive, informal, and fast method off-line communication. • An email address may consist of only the username if the user is on the same host or may have the form username@hostname or username@domainname. • Incoming mail is appended to a text file (the mailbox) named after the user-id in /var/mail (SVR4) or /var/spool/mail (Linux).

3. mail, elm, and pine • The earliest mail handling program is mail, but elm and pine are more powerful and user-friendly. • Viewed mail is often stored in $HOME/mbox, but elm and pine also use separate folders in $HOME/Mail. • You can reply to mail, forward, delete, or save a mail message with simple keystrokes.

4. pine: Yet Another Mail Program • You can search for a pattern, and also take suitable action on junk mail (spam). • Using pine, you can also defer dispatch of mail, maintain an address book and spell-checking your messages. • pine can be configured to automatically execute a series of keystrokes on startup. • Elm can be configured by editing the file $HOME/.elm/elmrc. Pine uses $HOME/.pinerc.

5. .signature and .forward: Two Important Fiels • You can redirect your mail by placing the desired email address in $HOME/.forward. romeo@yahoo.com • You can ensure that every message is accompanied by your personal details by placing them in the .signature file, which all mailers use by default. • Mail handling requires the work of three agencies:

6. How Mail Works • Mail user agent (MUA) – For reading and sending mail. • Mail transport agent (MTA) – For forwarding mail between machines. • Mail delivery agent (MDA) – For delivering mail to the recipients’ mailboxes. • In this three-tiered arrangement, the mail user agent (MUA) like pine or elm acts as the user’s front-end.

7. How Mail Works • Mail is transported using the Simple Mail Transfer Protocol (SMTP). SMTP hands over the message to the delivery agent. • Mail is fetched from a remote site with the Post Office Protocol (POP) often using a dialup line. • Netscape Messenger or Microsoft Outlook Express uses its own SMTP and POP client features to send mail and fetch it from POP server.

8. Netscape Messenger and Microsoft Outlook Express • Mail messages can be sorted in any sequence or moved to any folder by using the mouse. • Messenger can group messages that emanate from another as a thread. • Messenger and Outlook can view GIF and JPEG graphics inline along with the message.

9. Netscape Messenger and Microsoft Outlook Express • Eudora is another popular email program. • Web-based email services are more popular in these days. • The vacation command sends a predetermined message to everyone who sends a message to a user on vacation. • It is invoked from a user’s .forward file. For example, your .forward file might have:

10. Vacation: Going on Leave \eric, "|/usr/bin/vacation eric” which would send messages to you (assuming your login name was eric) and reply to any messages for “eric''.