How often do ISPs update their models?

Email filters are not something providers set once and walk away from. They're living systems, and they update on different timescales depending on what they're updating.

Machine learning models at providers like Gmail and Outlook retrain continuously, often incorporating new signal data daily or more. When a new spam wave hits, these models adapt fast. You won't get an announcement. It just happens.

Reputation databases update in real time. Complaint rates, spam trap hits, and engagement signals feed directly into your sender score as they happen. One bad campaign can move your reputation within hours.

Heuristic rules (the human-written ones that define specific patterns to catch) update more slowly. Weekly or monthly is typical, though a major phishing wave can push a rule update in hours if the team decides it's needed.

Policy-level changes are the one exception. When providers plan something that affects senders broadly, they usually announce in advance. The Yahoo Mail and Gmail 2024 sender requirements are a good example. Both companies gave months of notice before enforcement started.

What this means for you practically: your sending behavior matters more than any single filter update. If your engagement signals are healthy and your authentication is clean, most incremental model updates won't touch you. The senders who feel filter changes most are the ones already operating close to the edge. When the threshold shifts even slightly, they tip over it.

You don't need to change your strategy every time filters update. You need a strategy that holds up regardless. Send to people who want your emails, keep your list clean, and monitor your metrics. That approach stays solid through any update cycle.

Still if you've noticed a sudden dip in deliverability and want to rule out a blocklisting, you can run a quick check with our free blocklist checker. Or if something feels off and you want a second set of eyes, our SOS hotline is free.