Information
This policy setting controls whether Outlook displays the 'Add Signature Services' menu item. The recommended state for this setting is: Enabled. By default, users can select Add Signature Services (from the Signature Line drop-down menu on the Insert tab of the Ribbon in Excel, PowerPoint, and Word) to see a list of signature service providers on the Microsoft Office Web site. If your organization has policies that govern the use of external resources such as signature providers or Office Marketplace, allowing users to access the Add Signature Services menu item might enable them to violate those policies.
Solution
To implement the recommended configuration state, set the following Group Policy setting to Enabled. User Configuration\Administrative Templates\Microsoft Office 2016\Signing\Suppress External Signature Service Impact: Enabling this setting prevents users from adding a signature service from Microsoft Office.com, but should not otherwise cause significant usability issues for most users.