Configure Outlook object model prompt When accessing the Formula property of a UserProperty object
This `REG_DWORD` value controls how the Object Model Guard in classic Outlook responds when untrusted code accesses the protected `Formula` property of a `UserProperty` object.
since 0.9.8.11
Purpose
Show registry keys (1)
HKCU\software\policies\microsoft\office\16.0\outlook\security\promptoomformulaaccess
This REG_DWORD value controls how the Object Model Guard in classic Outlook responds when untrusted code accesses the protected Formula property of a UserProperty object. The property contains the formula associated with a custom Outlook property and can be used by combination or formula fields in custom forms. Because such formulas can reference address-information fields, Outlook treats access to this property as security-sensitive.
The value data has the following meanings:
0: Outlook automatically denies access.1: Outlook prompts the user to approve or deny each access attempt.2: Outlook automatically approves access.3: Outlook bases the prompt on the computer-security status reported through Windows Security Center. A prompt is normally displayed when antivirus software is inactive or out of date.
Notes
Security
A value of 2 lets untrusted programs access the Formula property without user confirmation. If a formula references address-information fields, this can permit programmatic access to that information.
A value of 0 blocks this specific access regardless of which program makes the request. The setting does not grant or revoke general Outlook, mailbox, or file permissions, and it does not change the protection applied to other Outlook object model properties or methods.
Possible side effects
Automatically denying access can disrupt custom Outlook forms, add-ins, or other automation solutions that depend on the Formula property. Repeated prompts can interrupt these workflows until the user approves or denies each request.
Notes
If the policy value is absent, behavior is determined by Outlook's other programmatic-access settings, including the overall Outlook object model security configuration and, where applicable, antivirus status.
This setting does not apply to new Outlook for Windows, which does not expose the classic Outlook object model.
Microsoft documentation
Microsoft Learn: Information about email security settings
Microsoft Learn: Protected Properties and Methods
Microsoft Learn: Security Behavior of the Outlook Object Model