This policy setting allows you to configure the list of low-risk file types. If the attachment is in the list of low-risk ...

This policy setting allows you to configure the list of low-risk file types. If the attachment is in the list of low-risk file types, Windows will not prompt the user before accessing the file, regardless of the file's zone information. This inclusion list overrides the list of high-risk file types built into Windows and has a lower precedence than the high-risk or medium-risk inclusion lists (where an extension is listed in more than one inclusion list).

If you enable this policy setting, you can specify file types that pose a low risk.

If you disable this policy setting, Windows uses its default trust logic.

If you do not configure this policy setting, Windows uses its default trust logic.