Configure Outlook object model prompt when responding to meeting and task requests
This `REG_DWORD` value controls the Outlook Object Model Guard when an untrusted program uses the Outlook object model's `Respond` method to respond to a meeting request or task request.
since 0.9.8.11
Purpose
Show registry keys (1)
HKCU\software\policies\microsoft\office\16.0\outlook\security\promptoommeetingtaskrequestresponse
This REG_DWORD value controls the Outlook Object Model Guard when an untrusted program uses the Outlook object model's Respond method to respond to a meeting request or task request. It applies to programmatically creating or sending such responses, not to responses initiated manually by the user.
The value data selects the guard behavior:
0: Outlook automatically denies the programmatic operation.1: Outlook prompts the user to approve each applicable access attempt.2: Outlook automatically approves the programmatic operation.3: Outlook bases the prompt on the computer's security status. It prompts when antivirus software is inactive or out of date.
If the policy value is absent, Outlook relies on the Programmatic Access setting in the Trust Center.
Notes
Security
Value 2 removes the protective prompt for this operation. An untrusted program can therefore initiate responses to meeting and task requests without user approval.
Value 0 blocks these programmatic responses without offering the user a choice. Value 1 requires an explicit user decision. With value 3, prompting depends on the antivirus status reported to Outlook; this mode does not itself establish that the calling program is trusted.
The setting is limited to responses made through the protected meeting-request and task-request methods of the Outlook object model. It does not control all Outlook automation or all forms of programmatic email sending.
Possible side effects
Value 0 can prevent applications and automation solutions from responding to meeting or task requests through the Outlook object model. Value 1 can interrupt unattended workflows with recurring security prompts. With value 3, behavior can change when Outlook detects a change in antivirus status.
Notes
This value is part of Outlook's per-user security policy. Outlook evaluates the Group Policy setting only when Outlook Security Mode is configured to use the Outlook Security Group Policy.
Trusted in-process add-ins can avoid invoking the Object Model Guard when they use objects derived exclusively from the trusted Application object supplied by Outlook. This setting is therefore primarily relevant to calls made by untrusted code.
Microsoft documentation
Microsoft Learn: Microsoft 365 Apps for Enterprise security baseline settings reference
Microsoft Learn: Information for administrators about email security settings in Outlook
Microsoft Learn: Outlook Object Model Security Warnings