Display Level 1 attachments

This policy setting controls whether Outlook blocks potentially dangerous attachments designated Level 1.
Outlook uses two levels of security to restrict users' access to files attached to e-mail messages or other items. Files with specific extensions can be categorized as Level 1 (users cannot view the file) or Level 2 (users can open the file after saving it to disk). Users can freely open files of types that are not categorized as Level 1 or Level 2.

If you enable this policy setting, Outlook users can gain access to Level 1 file type attachments by first saving the attachments to disk and then opening them, as with Level 2 attachments.

If you disable this policy setting, Level 1 attachments do not display under any circumstances.

If you do not configure this policy setting, Outlook completely blocks access to Level 1 files, and requires users to save Level 2 files to disk before opening them.

Supported on: At least Windows 7
Registry HiveHKEY_CURRENT_USER
Registry Pathsoftware\policies\microsoft\office\15.0\outlook\security
Value Nameshowlevel1attach
Value TypeREG_DWORD
Enabled Value1
Disabled Value0

outlk15.admx

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Administrative Templates (Users)