Inbound Versus Outbound Spam

Throughout this book, we use inbound and outbound to describe the direction of messages that your users receive and send, respectively. Inbound refers to messages (and spam) that end up in mailboxes on machines that you, as an administrator, manage. For example, these messages end up in IMAP or POP3 servers and are downloaded to an email client such as Mozilla or Microsoft Outlook. Outbound refers to messages that your users send from email clients, such as Microsoft Outlook Express or Lotus Notes, to remote users hosted on other mail systems. These messages (which hopefully are not spam!) pass through your mail systems on their way to their ultimate destination in some system not (necessarily) administrated by you. ...

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