In a Microsoft Skype for Business Server 2015 environment, you use the Skype for Business on Mac client that's in an external network to start a call with a Skype for Business client user. You may find that the value of Is From user internal always shows Yes on the Call detail recording (CDR) report. It's expected that the clients should be flagged correctly as external or internal on this report.
To fix this issue, install the July 2018 cumulative update 6.0.9319.534 for Skype for Business Server 2015, Web Components Server.
After you apply this update, you have to enable this change.
Note The Set-CsPlatformServiceSettingscmdlet gives you control to enable this change. You have to active this change by using the following cmdlet:
Set-CsPlatformServiceSettings – EnableExternalAccessCheck $true
If the caller uses the Skype for Business on Mac desktop client that connects an external network, the Is From User Internal flag will be marked as No.
If the user of the Skype for Business on Mac desktop client is a callee, or the client is a mobile client, it will keep the original behavior.
In addition, this update currently only addresses the issue for the sender side. For the value of Is To User Internal (receiver side), the issue is fixed in May 2019 cumulative update 6.0.9319.548 (CU9) for Skype for Business Server 2015.