Consider the following scenario:
User A is Enterprise Voice enabled in Microsoft Skype for Business Server 2015. User B is a PBX user who is configured to use a non E-164 number in the PBX/Gateway that's connected to the Skype for Business Mediation Server.
User A uses the Skype for Business for Mac, Skype for Business for iOS, or Skype for Business for Android client to start a call to user B through a non-E.164 (international public telecommunication number format) telephone number.
- User B answers the call successfully.
- User A hangs up the call. Then the call is saved in conversation history under the Calls tab.
- User A tries to call the telephone number again.
In this situation, the call fails.
This issue occurs because the call that's saved in conversation history doesn't have the "SIP URI user=phone" parameter string of the INVITE TO header. This causes the call not being routed to the destination telephone number.