Policy
Prevent users from customizing attachment security settings
This policy setting prevents users from overriding the set of attachments blocked by Outlook. If you enable this policy setting users will be prevented from overriding the set of attachments blocked by Outlook. Outlook also checks the "Level1Remove" registry key when this setting is specified. If you disable or do not configure this policy setting, users will be allowed to override the set of attachments blocked by Outlook.
1b1f37ff4d34 L_Preventusersfromcustomizingattachmentsecuritysettings Registry
Copy registry mappings
HKCU\software\policies\microsoft\office\16.0\outlook\disallowattachmentcustomization (enabled) = 1
HKCU\software\policies\microsoft\office\16.0\outlook\disallowattachmentcustomization (disabled) = 0 Policy notes
This policy setting prevents users from overriding the set of attachments blocked by Outlook. If you enable this policy setting users will be prevented from overriding the set of attachments blocked by Outlook. Outlook also checks the "Level1Remove" registry key when this setting is specified. If you disable or do not configure this policy setting, users will be allowed to override the set of attachments blocked by Outlook.