Computer Configuration > Administrative Templates > Skype for Business 2016 > Microsoft Lync Feature Policies
Machine
HKLM\software\policies\microsoft\office\16.0\lync
Requires the user to provide logon credentials for Microsoft Lync rather than automatically using the Windows credentials when Microsoft Lync authenticates the user using NTLM or Kerberos. If you enable this policy setting, Microsoft Lync requires the user to provide logon credentials. If you disable or do not configure this policy setting, Microsoft Lync authenticates the user based on the logon credentials for Windows. Note: You can configure this policy setting under both Computer Configuration and User Configuration, but the policy setting under Computer Configuration takes precedence.