Gmail Glitch Shows Forced Visibility Backfires
Jan 2026 Gmail filtering failure forced promotional emails into primary inboxes. Result: engagement up, but unsubscribes surged. What email marketers need to know.
Sarah Mitchell
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A two-day Gmail malfunction in January 2026 handed email marketers an accidental live experiment — and the results destroyed one of the industry's most stubborn myths: that landing in the Primary inbox is always better for your brand.
According to Spam Resource, the glitch gave Steven Lunniss, Director of Deliverability at email marketing platform Cordial, a rare window into what actually happens when promotional emails are forced into the Primary inbox. The finding: engagement went up slightly, but unsubscribes surged far more.
What Happened: Gmail's Filter Broke Down
On the morning of January 24, 2026, millions of Gmail users woke up to find their inboxes in chaos. The reliable order brought by Google's automatic email filters had suddenly vanished, with promotional and update emails flooding primary inboxes.
A server-side bug on January 24, 2026, caused Gmail's sorting algorithm to malfunction. The Promotions tab filter stopped working properly, allowing marketing emails to bypass their designated folder and appear in the Primary inbox.
The disruption didn't stop at misclassification. The glitch also temporarily affected Gmail's spam scanning, so some messages did not get scanned as they arrived, triggering warnings like "Gmail hasn't scanned this message for spam or harmful software."
The issue first appeared on Saturday, January 24, and lasted until Sunday, January 25. In a statement, a Google spokesperson said the company was "aware that some Gmail users are experiencing misclassification of emails in their inbox and additional spam warnings" and was "actively working to resolve the issue."
The Accidental Experiment: What the Data Revealed
Steven Lunniss, Director of Deliverability for Cordial, was able to answer a critical question thanks to this unexpected glitch: what happens to engagement and subscriber sentiment when email messages are unexpectedly redirected from the Promotions tab to the Primary inbox?
The answer was sobering for anyone who believes Primary placement is a silver bullet.
Engagement increased — but it wasn't much of a lift. And along with that modest engagement bump came an even greater boost in unsubscribes.
Lunniss calls this "forced engagement" — a dynamic where senders force messages in front of recipients who aren't always interested, or who are interested only on their own terms.
This pattern has a well-documented explanation. When promos sneak into Primary, unsubscribes can spike because people feel tricked or annoyed. In Promotions, fewer subscribers are surprised by promotional emails, so unsubscribe rates tend to be stable.

