In this chapter, you learned some of the basics of SMTP, IMAP4, POP3, and NNTP. You learned how to read the more common commands of these protocols and how to log the interaction between the server and client for troubleshooting purposes. You also learned how to filter messages to reduce SPAM in your environment. In the next chapter, you’ll learn the basics of connecting Exchange Server 2003 to other messaging systems using the X.400 Connector.