Voice and SMS Notification Delivery Issues via Certain U.S. Carrier Networks
This summary is created by Generative AI and may differ from the actual content.
Overview
Between January 14, 2026 at 17:05 UTC and January 15, 2026 at 10:27 UTC, telecom carriers experienced elevated delivery failures and delays for Voice and SMS notifications to US phone numbers on Verizon and AT&T routes. Customers outside the US may have also experienced delivery issues when sending Voice or SMS notifications to US numbers. Push notifications for Android and iOS, and WhatsApp notifications, were affected for users on Verizon mobile data who were not connected to Wi-Fi. Email, Slack, and other notification channels operated normally.
Impact
Estimated impact on customers, with delivery failures and delays for voice and SMS notifications to US phone numbers. However, the exact number of affected customers and the revenue impact are not specified in the postmortem.
Trigger
The incident was triggered by degradations on US routes, primarily affecting Verizon and AT&T customers, which resulted in increased delivery failures and delays for voice and SMS notifications to US phone numbers.
Detection
PagerDuty engineers observed elevated failure rates on internal telemetry and corroborating provider status updates indicating carrier-side issues, which led to the declaration of a major incident on January 14 at 19:56 UTC.
Resolution
PagerDuty responders kept the status page updated, closely monitored delivery logs, and maintained active communication with downstream notification delivery providers as carriers recovered. Voice and SMS delivery rates started to improve on January 15 at 05:46 UTC, and the incident responders resolved the incident at 10:27 UTC after confirming successful test notifications.
Root Cause
The root cause of the incident was the degradations on US routes, primarily affecting Verizon and AT&T customers, which was a carrier-level infrastructure issue outside of PagerDuty's control.