• user agents (clients)
• transport agents (qmail, exim, sendmail)
• delivery agents (procmail, sendmail add ons)
• Storing messages (/var/spool/mail/ or a DB)
• Access agents (imapd pop3)
• Mail submission agents (even sendmail, again)
• Relays and spam
• aliases and forwarding

• Understand basic configuration of sendmail, procmail
• Understand the roles of the different agents
• How to read a mail header.

/var/spool/mail/
/etc/sendmail.*
/etc/aliases and/or /etc/mail/aliases
~/.forward
Commands:
/usr/sbin/sendmail -d0.1 -bt < /dev/null
nslookup (set q=mx)
mailstat
listserv/majordomo

• How do you prevent spam?
• What is the best way to create the sendmail.cf configuration file?
• How would you install something like majordomo?
• What is a trusted user?
• What can procmail do for you?
• What advantages do postfix and qmail have over sendmail, if any?
• What sites offer you protection against spam?
• What is a RBL?
• What is the purpose of mailmain, squirrel mail?
• What are the plusses and minuses of various spam filters?

• Mail Abuse Prevention System (MAPS) Which works on a RBL
• Sendmail Anti-spam configuration
• Fight Spam on the Internet!
• Hardening Sendmail
• A Plan For Spam: Bayesian Filtering
• Procmail: Getting Rid of Spam
• Sendmail Anti-Spam modifications
• Sendmail Home Page
• SMTPD to Prevent Spam
• Exim MTA homepage
• Procmail Homepage
• PostFix
• Mailman, GNU Mailing List Manager
• SquirrelMail-Webmail for Nuts!
• Majordomo email list server
• Email Filter Reviews