If you need to get voicemail notification for other extensions, the only way is subscribing for the /restapi/v1.0/account/~/telephony/sessions?direction=Inbound event notification. Then when you catch the event, parse it as shown in the example code below

...

// received thru your Webhook callback endpoint

var party = req.body.body.parties[

if (party.extensionId){

  if(party.status.code == "Disconnected"){

    if (party.status.reason == 'Voicemail'){

      // there is a voice mail

      ...

    }

  }

}

Hi @Phong Vu thank you. I will check and reach here.