In Lync Server 2010 when a user configured simultaneously ringing in Lync, and they receive a call when their mobile phone is turned off, the call will automatically be answered (or redirected) by the carriers voicemail.
Well those times of bad voicemail are now over, with Lync Server 2013 a admin can opt to have the users business-related calls routed to their corporate voice mail system. This is done by a timer that we can configure (its off by default), and if the call is answered by the carrier’s voice mail within the range of time, Lync Server 2013 will disconnect the call from the operators voice mail system, while the user’s Lync clients (Lync or LPE) continue to ring and the caller is automatically routed to the user’s Exchange UM voice mail.
This is configured on the users Voice Policy and the only way to enable it is via the Lync Config Shell and the command Set-CsVoicePolicy
So by default it will look like this and we can see that its set to False
By running the command:
Set-CsVoicePolicy Global -EnableVoiceMailEscapeTimer $true – PSTNVoicemailEscapeTimer 2000
We now change it to True and to wait 2 seconds, and if the call is answered before the 2 seconds the call will be disconnected and still ring on the Lync endpoints untill the configured time out on the Lync client kicks in and then the call is sent to Exchange UM.