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:

• Increasing Capacity: Engineers increased resources for the affected services. This included general capacity increases for the spam classification services and related backend components. One specific action was a significant, emergency increase of resources for a backend service responsible for abuse detection.
• Reducing System Load: To alleviate pressure on the systems, engineers temporarily disabled certain functionalities to free up headroom for the spam classification services to recover.
• Tuning Retry Logic: To address the cascading issues caused by excessive retries, the team rolled out changes to the retry logic in the mail delivery system.

Google is committed to preventing recurrence by implementing the following action items:

• Enhanced Emergency Controls : We are enhancing our emergency control mechanisms and accelerating mitigation protocols to facilitate rapid recovery through temporary manual traffic tuning overrides during similar service disruptions.
• Improved Load shedding: Implement criticality-aware load shedding across the spam system to protect services and subsystems during overload.
• Tune Message Delivery Retries: Optimize the retry logic in the mail delivery system to avoid overwhelming downstream services.
• Improved Deadline Propagation: Ensure that service deadlines are correctly propagated and honored across the entire spam classification stack.
• Reshape Processing Tasks: Increase the memory and compute resources allocated to individual anti-abuse systems to handle spikes more gracefully.

Detailed Description of Impact

On Saturday, 24 January 2026 from 05:02 to 09:55 US/Pacific, many Gmail messages experienced elevated failure rates in spam checking. Affected users saw a banner indicating their messages were not scanned for spam and saw some messages not labelled accordingly as promotional and social, and experienced delivery delays, generally up to 10 minutes.

User Experience:

• Warning Banners: Users received a banner on incoming messages stating: "Be careful with this message. Gmail hasn't scanned this message for spam, unverified senders, or harmful software."
• Delivery Delays: Impacted messages experienced delivery delays, up to 10 minutes. However, there were no instances of lost emails or erroneously delivered during this period.
• Message Labeling: Users may have noticed that promotional or social labels were not correctly applied during the disruption.

Preliminary Incident Report

We apologize for the inconvenience this service disruption may have caused. We would like to provide some information about this incident below. Please note, this information is based on our best knowledge at the time of posting and is subject to change as our investigation continues. A final Incident Report with preventative actions will be posted once our investigation is complete. If you have experienced an impact outside of what is listed below, please reach out to Google Workspace Support using the help article https://support-google-com.mygreatmarket.com/a/answer/1047213.

Date/Time of the Issue (All time US/Pacific)

Incident Start: 24 January 2026 05:02

Incident End: 24 January 2026 09:55

Duration: 4 hours and 53 minutes

Summary

On Saturday, 24 January 2026, Gmail experienced elevated email delivery time and reduction in the number of emails that were checked for spam for a duration of 4 hours and 53 minutes. Affected users saw email delivery delays and a banner indicating their messages were not scanned for spam on some email. We understand how important Gmail's reliability is for our users and sincerely apologize for the impact this disruption may have caused to your organization. We are taking immediate steps to improve our systems' performance and availability to prevent recurrence.

Preliminary 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 when a backend component within Gmail's mail processing pipeline, which is responsible for analyzing incoming messages, demonstrated increased latency.
• 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 a subset of Gmail users experiencing message delivery delays, which were generally 10 minutes or less.

Google engineers are performing a full root cause analysis and will provide additional information once it is available.

Remediation

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:

• Increasing Capacity: Google engineers increased resources for the affected services. This included general capacity increases for the spam classification services and related backend components. One specific action was a significant, emergency increase of resources for a backend service responsible for abuse detection.
• Reducing System Load: To alleviate pressure on the systems, Google engineers temporarily disabled certain non essential functionality to increase headroom for the spam classification services. Google engineers also deployed an emergency configuration to the spam classification services that disabled a specific message analysis feature, which was expected to lower the error rate.
• Tuning Retry Logic: To address the cascading issues caused by excessive retries, the team rolled out changes to the retry logic in the mail delivery system. This tuning involved reducing the number of retries and implementing emergency rate limiting for retries, applied at the top of the stack. This approach helped to quickly shed load, allowing backend services to recover.

Description of Impact

On Saturday, 24 January 2026 from 05:02 to 09:55 US/Pacific, many Gmail messages experienced elevated failure rates in spam checking. Affected users saw a banner indicating their messages were not scanned for spam and experienced delivery delays, generally 10 minutes or less.

User Experience:

• Warning Banners: Users received a banner on incoming messages stating: "Be careful with this message. Gmail hasn't scanned this message for spam, unverified senders, or harmful software."
• Delivery Delays: Impacted messages experienced delivery delays, majorly between 5 to 10 minutes. However, there were no instances of lost emails or erroneously delivered during this period.
• Some users may have noticed that promotional or social labels were not correctly applied during the disruption.

Summary : Some Gmail users experienced a misclassification of emails in their inbox, additional spam warnings, and delays in receiving email.

Description : The issue with Gmail email classification is resolved as of Saturday, 2026-01-24 09:55 US/Pacific.

We will publish an analysis of this incident once we have completed our internal investigation.

We thank you for your patience while we worked on resolving the issue.

Diagnosis / Customer Symptoms : Some Gmail users experienced a misclassification of emails in their inbox, delays in receiving email. Additionally, misclassified spam warnings from the incident may persist for existing messages received before the issue resolution.

Description We are experiencing an issue with Gmail beginning on Saturday, 2026-01-24 05:02 US/Pacific.

We are aware that some Gmail users are experiencing misclassification of emails in their inbox and additional spam warnings. We are actively working to resolve the issue. As always, we encourage users to follow standard best practices when engaging with messages from unknown senders.

We will provide an update by Saturday, 2026-01-24 17:00 US/Pacific with current details.

Description We are experiencing an issue with Gmail beginning on Saturday, 2026-01-24 05:02 US/Pacific.

We are aware that some Gmail users are experiencing misclassification of emails in their inbox and additional spam warnings. We are actively working to resolve the issue. As always, we encourage users to follow standard best practices when engaging with messages from unknown senders.

We will provide an update by Saturday, 2026-01-24 14:00 US/Pacific with current details.

Description We are experiencing an issue with Gmail beginning on Saturday, 2026-01-24 05:02 US/Pacific.

We are aware that some Gmail users are experiencing misclassification of emails in their inbox and additional spam warnings. We are actively working to resolve the issue. As always, we encourage users to follow standard best practices when engaging with messages from unknown senders.

We will provide an update by Saturday, 2026-01-24 13:30 US/Pacific with current details.

Description We are experiencing an issue with Gmail beginning on Saturday, 2026-01-24 05:02 US/Pacific.

We are aware that some Gmail users are experiencing misclassification of emails in their inbox and additional spam warnings. We are actively working to resolve the issue. As always, we encourage users to follow standard best practices when engaging with messages from unknown senders.

We will provide an update by Saturday, 2026-01-24 12:00 US/Pacific with current details.

Description We are experiencing an issue with Gmail beginning on Saturday, 2026-01-24 05:02 US/Pacific.

We are aware that some Gmail users are experiencing misclassification of emails in their inbox and additional spam warnings. We are actively working to resolve the issue. As always, we encourage users to follow standard best practices when engaging with messages from unknown senders.

We will provide an update by Saturday, 2026-01-24 11:00 US/Pacific with current details

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 might experience the following banner: “Be careful with this message. Gmail hasn't scanned this message for spam, unverified senders, or harmful software.”

We advise the users to be extra diligent in lieu of missing spam checks.

Our engineering team is investigating the issue.

We will provide an update by Saturday, 2026-01-24 09:30 with current details.