This will disable the IM for the specific user, for massive, you may use GPO login script to deploy for set of groups. reg add HKLM\Software\Policies\Microsoft\Office\15.0\Lync /v DisableIM /t REG_DWORD /d 1 /f change to /d 0 to enable.
This will disable the IM for the specific user, for massive, you may use GPO login script to deploy for set of groups. reg add HKLM\Software\Policies\Microsoft\Office\15.0\Lync /v DisableIM /t REG_DWORD /d 1 /f change to /d 0 to enable.
Hany Taha 