Users who’re not Enterprise Voice enabled can dial out when PreventPSTNTollBypass is true in Skype for Business Server 2019 and 2015

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Applies To

Skype for Business Server 2019 Skype for Business Server 2015

Symptoms

When the PreventPSTNTollBypass parameter in voice policy is set to true and the AllowNonEnterpriseVoiceUsersToDialOut parameter in conferencing policy is set to false in a Microsoft Skype For Business Server 2019 or Skype for Business Server 2015 environment, users who’re not enabled for Enterprise Voice unexpectedly can dial out from a conference.

Resolution

To fix this issue, install one of the following updates:

For Skype for Business Server 2019, install the December 2019 cumulative update 7.0.2046.151 for Skype for Business Server 2019, Front End Server and Edge Server.
For Skype for Business Server 2015, install the May 2020 cumulative update 6.0.9319.580 for Skype for Business Server 2015, Front End Server and Edge Server.