Missed call notification because of wrong handling of SIP header in Skype for Business Server 2019 and 2015 (KB4583494)

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Applies To

Skype for Business Server 2019 Skype for Business Server 2015

Symptoms

In Microsoft Skype for Business Server 2019 or Skype for Business Server 2015, a Skype for Business client user still receives a missed call notification even though the call was answered by other telephony systems (for example, the Alcatel telephony system).

Resolution

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

The September 2020 cumulative update 7.0.2046.244 for Skype for Business Server 2019, Front End Server and Edge Server.
The August 2021 cumulative update 6.0.9319.619 for Skype for Business Server 2015, Front End Server and Edge Server.