What the Gmail spam filter glitch means for lifecycle teams

On January 24-25, 2026, Gmail's spam filtering and inbox sorting systems failed for a significant portion of users. Emails bypassed spam filters entirely, promotional messages flooded primary inboxes, and delivery delays caused time-sensitive messages like two-factor authentication codes to arrive late or expired.

For lifecycle marketers, this kind of incident is a reminder that deliverability is never fully in your control, and that building resilient programs means preparing for the unexpected.

What happened

Gmail's automated scanning systems stopped working for many users over the weekend. Affected inboxes displayed a warning banner stating that messages had not been scanned for spam, unverified senders, or harmful software. At the same time, Gmail's tab sorting broke down, routing promotional and social emails directly into the Primary inbox instead of their usual secondary tabs.

The result was inbox chaos. Users who rely on Gmail's filtering to manage email volume suddenly faced an overwhelming mix of marketing messages, social notifications, and legitimate correspondence, all competing for attention in the same view. Google acknowledged the incident on its Workspace Status Dashboard and advised users to be "extra diligent" while engineering teams worked on a resolution.

Delivery delays compounded the problem. Reports on Downdetector indicated delays of ten minutes or more, which proved especially disruptive for email-based two-factor authentication. Security codes with short validity windows arrived after they had already expired, locking users out of accounts.

Why this matters for lifecycle marketers

Gmail is the largest email provider in the world. When its systems fail, the impact on email programs is immediate and widespread.

Engagement metrics become unreliable. During an outage like this, open and click behavior can spike or drop in ways that do not reflect subscriber intent. Promotional emails landing in Primary may see unusual engagement, while legitimate transactional messages may go unnoticed in the flood. Any A/B tests or performance analysis running during this window should be interpreted with caution.

Transactional email timing is at risk. Lifecycle programs often depend on time-sensitive messages, from order confirmations to password resets to authentication codes. A ten-minute delay can mean the difference between a smooth user experience and a frustrated customer locked out of their account.

Subscriber trust can erode. When inboxes are flooded with unwanted messages, users may become more aggressive about unsubscribing or marking emails as spam, even from senders they normally engage with. The association between inbox frustration and your brand may not be rational, but it is real. Understanding how ISPs judge your emails based on reputation and engagement signals is critical context here.

What lifecycle teams should do

Monitor your own metrics closely after major inbox provider incidents. Look for unusual patterns in engagement, complaints, or unsubscribes that do not align with your typical performance. If you see anomalies, note the timing and do not make strategic decisions based on data from affected windows. Our post on monitoring and troubleshooting deliverability covers how to use seed tests, blocklist checks, and analytics to diagnose issues.

Audit your transactional email flows. Identify messages that are time-sensitive and consider whether you have fallback mechanisms in place. For authentication codes, the National Institute of Standards and Technology (NIST) recommends app-based authenticators over email or SMS-based 2FA as a more reliable and secure alternative.

Diversify your communication channels where appropriate. Email remains the backbone of most lifecycle programs, but SMS, push notifications, and in-app messaging can provide backup paths for critical communications. This is especially important for transactional messages where delivery timing matters.

Document incidents like this for internal stakeholders. When deliverability or engagement dips due to inbox provider issues, having a record of external events helps explain performance to leadership and prevents overreaction to temporary anomalies.

The bigger picture

Gmail's filtering systems are remarkably reliable, which is exactly why failures like this are so disruptive when they occur. Lifecycle teams benefit from that reliability every day, but they cannot depend on it absolutely.

Building resilience into your email program means accepting that inbox providers, ESPs, and infrastructure can all fail at some point. The best programs are designed to recover quickly, communicate clearly, and maintain subscriber trust even when external systems do not cooperate.

Incidents like this weekend's Gmail glitch are rare, but they are not unpredictable. Treating deliverability as a continuous practice rather than a one-time setup is what separates programs that weather these moments from those that suffer lasting damage. For a deeper dive into the foundations, explore our full deliverability series.