Gmail users might see banners indicating missing spam checks. We are experiencing an issue with Gmail beginning on Saturday, 2026-01-24 05:02 US/Pacific. Users...

What caused it: Gmail's root cause analysis

# Incident Report Summary On Saturday, 24 January 2026, beginning at 05:02 US/Pacific, Gmail experienced high failure rates in spam checking for a duration of 4 hours and 53 minutes. Affected users saw a banner indicating their messages were not scanned for spam and saw some messages not labelled accordingly as promotional and social. Following recovery of the above-mentioned issues, some Gmail users experienced delivery delays up to 10 minutes or less. This issue was resolved for most users by 09:55 US/Pacific on Saturday, 24 January 2026. We recognize the critical nature of Gmail's reliability to your operations and extend our sincere apologies for any disruption this incident may have caused to your organization. We are implementing immediate measures to enhance system performance and stability to prevent such an occurrence from happening again. Root Cause This incident was caused by an overload of Gmail's spam checking systems, which in turn was triggered by a temporary failure in a backend service. This led to a cascading failure due to excessive retries. The sequence of events leading to customer impact was as follows: * Trigger: The incident began with a temporary error in a backend component within Gmail's mail processing pipeline, which is responsible for analyzing incoming messages. * Cause: While the initial error was temporary, the system's response to it caused the impact. A retry mechanism, designed to handle such transient failures, generated a massive and sustained volume of retry traffic. This cascading retry storm overwhelmed the capacity of multiple backend systems for several hours. * Effect: The overload on the spam checking services and related systems meant that there were mail delivery delays and not all incoming mail was fully classified. To protect users from potentially malicious content, Gmail displayed a warning banner on the affected emails. This issue resulted in some Gmail users experiencing message delivery delays, which were generally 10 minutes or less. Remediation and Prevention Google engineers were alerted to the issue via automated monitoring at 05:12 US/Pacific on Saturday, 24 January 2026, and immediately began an investigation. The investigation identified high error rates and latency across the classification pipeline. To mitigate the impact of the incident, Google engineers implemented several measures focused on increasing system capacity and temporarily reducing load. The key mitigation actions taken were: * In...

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