When Lync connects to the server it supports various authentication mechanisms. This policy allows the user to specify whether Digest and Basic authentication are supported. Disabled (default): NTLM/Kerberos/TLS-DSK/Digest/Basic Enabled: Authentication mechanisms: NTLM/Kerberos/TLS-DSK Gal Download: Requires HTTPS if user is not logged in as an internal user.
Solution
Policy Path: Skype for Business 2016\Microsoft Lync Feature Policies Policy Setting Name: Configure SIP security mode