This policy setting controls whether Outlook will use remote certificate authority information in a secure email message to validate that its certificate is trusted.
If you enable this setting, you'll allow the operating system to access remote network locations specified in a certificate for validation.
If you disable or don't configure this setting, retrieval of remote Certificate Authority Information won't be allowed, and only stored certificates will be used for authentication.
| Registry Hive | HKEY_CURRENT_USER |
| Registry Path | software\policies\microsoft\office\16.0\outlook\security |
| Value Name | enableaiacertextension |
| Value Type | REG_DWORD |
| Enabled Value | 1 |
| Disabled Value | 0 |