The Publish to Global Address List (GAL) button must be disabled in Outlook.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-223355	O365-OU-000010	SV-223355r961863_rule		Medium

Description

This policy setting controls whether Outlook users can publish e-mail certificates to the Global Address List (GAL). If you enable this policy setting, the "Publish to GAL" button does not display in the "E-mail Security" section of the Trust Center. If you disable or do not configure this policy setting, Outlook users can publish their e-mail certificates to the GAL through the "E-mail Security" section of the Trust Center.

STIG	Date
Microsoft Office 365 ProPlus Security Technical Implementation Guide	2025-03-05

Details

Check Text (C-25028r811488_chk)

Verify the policy value for User Configuration >> Administrative Templates >> Microsoft Outlook 2016 >> Security >> Cryptography >> Do not display 'Publish to GAL' button is set to "Enabled".

Use the Windows Registry to navigate to the following key:

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

If the value for publishtogaldisabled is REG_DWORD = 1, this is not a finding.

Fix Text (F-25016r442285_fix)

Set the policy value for User Configuration >> Administrative Templates >> Microsoft Outlook 2016 >> Security >> Cryptography >> Do not display 'Publish to GAL' button to "Enabled".