Outlook minimum encryption key length settings must be set.

Severity	Group ID	Group Title	Version	Rule ID	Date	STIG Version
medium	V-228474	SRG-APP-000514	DTOO316	SV-228474r508021_rule	2022-03-11	2

Description
This policy setting allows you to set the minimum key length for an encrypted e-mail message. If you enable this policy setting, you may set the minimum key length for an encrypted e-mail message. Outlook will display a warning dialog if the user tries to send a message using an encryption key that is below the minimum encryption key value set. The user can still choose to ignore the warning and send using the encryption key originally chosen. If you disable or do not configure this policy setting, a dialog warning will be shown to the user if the user attempts to send a message using encryption. The user can still choose to ignore the warning and send using the encryption key originally chosen.

Description

This policy setting allows you to set the minimum key length for an encrypted e-mail message. If you enable this policy setting, you may set the minimum key length for an encrypted e-mail message. Outlook will display a warning dialog if the user tries to send a message using an encryption key that is below the minimum encryption key value set. The user can still choose to ignore the warning and send using the encryption key originally chosen. If you disable or do not configure this policy setting, a dialog warning will be shown to the user if the user attempts to send a message using encryption. The user can still choose to ignore the warning and send using the encryption key originally chosen.

ℹ️ Check
Verify the policy value for User Configuration -> Administrative Templates -> Microsoft Outlook 2016 -> Security -> Cryptography "Minimum encryption settings" is set to "Enabled: 168 bits". 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 MinEncKey is REG_DWORD = a8 (hex) or 168 (decimal), this is not a finding.

ℹ️ Check

Verify the policy value for User Configuration -> Administrative Templates -> Microsoft Outlook 2016 -> Security -> Cryptography "Minimum encryption settings" is set to "Enabled: 168 bits". 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 MinEncKey is REG_DWORD = a8 (hex) or 168 (decimal), this is not a finding.

✔️ Fix
Set the policy value for User Configuration -> Administrative Templates -> Microsoft Outlook 2016 -> Security -> Cryptography "Minimum encryption settings" to "Enabled: 168 bits".