Microsoft 365 Alert – Service Degradation – Microsoft Teams – Users were intermittently experiencing one-way audio for some calls using any Microsoft Teams client – RESOLVED

Announcements Arpan Das

26/05/2025 08:48:00 AM

NHSmail Reference: INC46538072

Microsoft Reference: TM1080572

Issue Status: RESOLVED

Issue Description: Users are intermittently experiencing one-way audio for some calls using any Microsoft Teams client.

More info: Impact was specific to outbound audio to Public Switched Telephone Network (PSTN) destinations.

Final Update: 26/05/2025 08:48:00 AM – After redirecting the affected traffic through alternate infrastructure to repair this issue, Microsoft have confirmed through testing with a subset of users that impact was successfully remediated.

Scope of impact: Your organization was impacted by this event, and impact was limited to PSTN calls.

Root cause: A section of networking infrastructure responsible for regulating the audio to Public Switched Telephone Network (PSTN) destinations wasn’t routing the call traffic as expected.

Next Steps: Microsoft are continuing to investigate why networking infrastructure responsible for regulating the audio to PSTN destinations was not routing the call traffic as expected to better understand and prevent similar future impact.