Missing root certificates: registry value sigstatusnotrustdecisionUserHKCU\software\policies\microsoft\office\16.0\outlook\security

Policy ID: L_Missingrootcertificates
Scope: User Configuration
Supported on: At least Windows Server 2008 R2 or Windows 7
Source: Microsoft 365 Apps / Office Administrative Templates (version 5568.1000)
Category: Microsoft Outlook 2016 › Security › Cryptography › Signature Status dialog box

Registry

sigstatusnotrustdecision

REG_DWORDUser

HKCU\software\policies\microsoft\office\16.0\outlook\security Current key

Enabled value: Depends on the option value
Element: Indicate a missing root certificate as a(n):

Options
Item	Stored value
Neither error nor warning	0
Warning	1
Error	2

Apply with .reg · CMD · PowerShell

.reg

Windows Registry Editor Version 5.00

[HKEY_CURRENT_USER\software\policies\microsoft\office\16.0\outlook\security]

; Options (use only one)
; Neither error nor warning
"sigstatusnotrustdecision"=dword:00000000
; Warning
"sigstatusnotrustdecision"=dword:00000001
; Error
"sigstatusnotrustdecision"=dword:00000002

CMD

:: Options (use only one)

:: Neither error nor warning
reg add "HKCU\software\policies\microsoft\office\16.0\outlook\security" /v "sigstatusnotrustdecision" /t REG_DWORD /d 0 /f
:: Warning
reg add "HKCU\software\policies\microsoft\office\16.0\outlook\security" /v "sigstatusnotrustdecision" /t REG_DWORD /d 1 /f
:: Error
reg add "HKCU\software\policies\microsoft\office\16.0\outlook\security" /v "sigstatusnotrustdecision" /t REG_DWORD /d 2 /f

PowerShell

# Common: create the key
New-Item -Path 'HKCU:\software\policies\microsoft\office\16.0\outlook\security' -Force | Out-Null

# Options (use only one)
# Neither error nor warning
New-ItemProperty -Path 'HKCU:\software\policies\microsoft\office\16.0\outlook\security' -Name 'sigstatusnotrustdecision' -PropertyType DWord -Value 0 -Force | Out-Null
# Warning
New-ItemProperty -Path 'HKCU:\software\policies\microsoft\office\16.0\outlook\security' -Name 'sigstatusnotrustdecision' -PropertyType DWord -Value 1 -Force | Out-Null
# Error
New-ItemProperty -Path 'HKCU:\software\policies\microsoft\office\16.0\outlook\security' -Name 'sigstatusnotrustdecision' -PropertyType DWord -Value 2 -Force | Out-Null