Check e-mail addresses against addresses of certificates being used must be disallowed.

This policy setting controls whether Outlook verifies the user's e-mail address with the address associated with the certificate used for signing. If you enable this policy setting, users can send messages signed with certificates that do not match their e-mail addresses. If you disable or do not configure this policy setting, Outlook verifies that the user's e-mail address matches the certificate being used for signing.

Verify the policy value for User Configuration -> Administrative Templates -> Microsoft Outlook 2016 -> Security -> Cryptography "Do not check e-mail address against address of certificates being used" is set to "Enabled".

Procedure: Use the Windows Registry Editor to navigate to the following key:

HKCU\Software\Policies\Microsoft\Office\16.0\outlook\security

Criteria: If the value SupressNameChecks is REG_DWORD = 1, this is not a finding.

Set the policy value for User Configuration -> Administrative Templates -> Microsoft Outlook 2016 -> Security -> Cryptography "Do not check e-mail address against address of certificates being used" to "Enabled".