1. Email Filter
   1. Software used to organize and apply configured filters to incoming and outgoing emails.
2. Uses:
   1. Organization and Prioritization of Important Messages
   2. Anti-Spam
   3. Data Loss Prevention (DLP)
   4. Malware Removal
3. Methods:
   1. Email filters may be installed:
      1. Within the email program
      2. Within the web browser, but external to the email program
      3. On the host machine, external to both the email program and web browser
   2. Email service providers, if external to the organization, may also separately deploy email filtering techniques
   3. Mail filters can operate inbound or outbound
      1. Inbound:
         1. Scanning messages from the Internet addressed to users protected by the filtering system
      2. Outbound:
         1. Scanning email messages from local users before any potentially harmful messages can be delivered to others on the Internet.
         2. Required for DLP Policies
         3. Methods:
            1. Transparent SMTP Proxying:
            2. Email traffic is intercepted and filtered via a transparent proxy within the network.
            3. Mail Servers