1. Email WeeSan Lee http://www.cs.ucr.edu/~weesan/cs183/

2. Roadmap Introduction Mail System Architecture Email Headers Sendmail Debugging Aliases Forwarding Procmail Q&A

3. Introduction MTA (port 25) MSA (port 587) MUA Eudora MUA pine MUA mail The Internet MTA (port 25) LDA procmail Message store MUA mail MUA pine AA Imapd, pop3 MUA Outlook

4. Introduction (cont) A mail system consists of:  MUA – Mail User Agent Lets users read and compose email, eg. Mail, Pine, Eudora, Outlook  MTA – Mail Transport Agent Routes emails among machines, eg. Sendmail, Postfix Speaks SMTP (Simple Mail Transport Protocol)  MSA – Mail Submission Agent Accepting emails from MUA, eg. Sendmail  LDA – Local Delivery Agent Places emails to a local message store, eg. Procmail /var/spool/mail/username  AA – Access Agent Connects MUA to message store, eg. POP3, IMAP Question: What are the differences between POP3 and IMAP?

5. Mail System Architecture Incoming SMTP server  For accepting incoming emails with spam filters Outgoing SMTP server  For sending outgoing emails IMAP or POP3 server  For retrieving emails Message Store  /var/spool/mail/username  /home/username/mail/INBOX

6. E-mail Header  Attribute: value  Eg. From: weesan@cs.ucr.eduweesan@cs.ucr.edu Bcc: bill.gates@microsoft.combill.gates@microsoft.com  Header starts with X- will be ignored, eg. X-Spam-Flag: YES Body  7-bit ASCII text  Question: How are binary data sent over emails?

7. Sendmail Both a MTA (port 25) and MSA (port 587) Configuration file  /etc/mail/sendmail.cf Mail queue  /var/spool/mqueue/

8. Debugging mail  $ cal | mail -s “test” weesan@cs.ucr.eduweesan@cs.ucr.edu sendmail -oi -t  $ cat | sendmail -oi –t  From: weesan@cs.ucr.eduweesan@cs.ucr.edu  To: bill.gates@microsoft.combill.gates@microsoft.com  Subject: Hi Bill  Linux is better  -WeeSan  ^D

9. Debugging (cont) telnet  $ telnet mail.cs.ucr.edu 25  …  220 esmtp.cs.ucr.edu ESMTP Postfix  mail from: weesan@cs.ucr.edu  250 Ok  rcpt to: bill.gates@microsoft.com  250 Ok  data  354 End data with.  Subject: Hi Bill  Linux is better :) .  250 Ok: queued as F1C832AFBE4  quit  221 Bye  Connection closed by foreign host.

10. /etc/aliases or /etc/mail/aliases Allows users to be referred by multiple names Used by mailing list $ cat /etc/aliases | grep weesan  root: weesan, weesan@email.comweesan@email.com To rehash aliases  $ newaliases

11. ~/.forward $ cat ~/.forward  \weesan  weesan@email.com

12. ~/.procmailrc # For spam :0 * (^Subject:.*\[SPAM\]|X-Spam-Flag: YES) INBOX.spam # Another type of spam :0 * ^From:.*bill.gates@microsoft.com /dev/null

13. ~/.procmailrc # SMS myself :0 c * ^From:.*myboss@ucr.edu | (formail -c -XFrom: -XSubject: ; echo "To: $MY_CELL") | $SENDMAIL -oi -t

14. ~/.procmailrc # UCR Systems support emails :0 * ^Subject:.*(New Ticket|Ticket Assigned) { :0 c INBOX.systems :0 | (formail -c -XFrom: -XSubject: ; echo "To: $MY_CELL") | $SENDMAIL -oi -t }

15. Reference LAH  Ch 18: Electronic Mail http://www.sendmail.org/ http://www.procmail.org/ http://www.imap.org/