Email is extremely important for most individuals and businesses today, and Linux can function as part of your network's email system. You can use a Linux SMTP server, such as sendmail or Postfix, to handle incoming mail instead of or in addition to a Microsoft Exchange server, and you can use a Linux POP or IMAP server to deliver mail to Windows, Mac OS, Linux, and other clients. One of the ways you can employ a Linux mail server is as a screening system for spam and worms. You can do this whether Linux is your sole mail server or it's just part of a larger mail solution. Finally, a tool called Fetchmail enables you to retrieve mail from a remote pull mail server and deliver it using your own pull mail server or deliver it via SMTP to another server.