Quite a while ago a customer wished to block Lync Mobile on iOS and Android platforms as it didn’t conform to their corporate device policy, sadly with Lync Server 2010 couldn’t do this out-of-the-box and could only be done by blocking the specific user-agent ID’s via a iRule on F5 or on TMG via a HTTP filter.
However it seem there is a solution in Lync Server 2013 within the client version policy (not somewhere I go very often)
