Policy
Missing root certificates
This policy setting controls how Outlook functions when a root certificate is missing. If you enable this policy setting, you can choose from three options that determine how Outlook functions when a root certificate is missing. - Neither Error nor Warning. This option displays neither an error nor a warning, and enforces the default configuration in Outlook. - Warning. This option ensures that Outlook displays a warning message when a root certificate is missing. - Error. This option ensures that Outlook displays an error message when a root certificate is missing. If you don't configure this policy setting, users will see an error when a root certificate is missing.
21252b70d7d5 L_Missingrootcertificates Registry
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HKCU\software\policies\microsoft\office\16.0\outlook\security\sigstatusnotrustdecisionPolicy notes
This policy setting controls how Outlook functions when a root certificate is missing. If you enable this policy setting, you can choose from three options that determine how Outlook functions when a root certificate is missing. - Neither Error nor Warning. This option displays neither an error nor a warning, and enforces the default configuration in Outlook. - Warning. This option ensures that Outlook displays a warning message when a root certificate is missing. - Error. This option ensures that Outlook displays an error message when a root certificate is missing. If you don't configure this policy setting, users will see an error when a root certificate is missing.