This policy setting controls whether the Junk E-mail Filter is enabled in Outlook. The Junk E-mail Filter in Outlook is designed to intercept the most obvious junk e-mail, or spam, and send it to users' Junk E-mail folders. The filter evaluates each incoming message based on several factors, including the time when the message was sent and the content of the message. The filter does not single out any particular sender or message type, but instead analyzes each message based on its content and structure to discover whether or not it is probably spam.
If you enable this policy setting, junk e-mail filtering in Outlook is turned off entirely, in addition to hiding the filtering controls from users. In addition, you can use the "Junk E-mail Protection level" policy setting to preset a filtering level and prevent users from changing it. Note - This policy setting does not affect the configuration of the Microsoft Exchange Server Intelligent Message Filter (IMF), which provides server-level junk e-mail filtering.
If you disable or do not configure this policy setting, the Junk E-mail Filter in Outlook is enabled.