How can you measure deliverability drift post-update?
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Drift is sneaky because it doesn't hit you all at once. It's the gradual decline (or improvement) that happens over days or weeks after a provider update. One day your inbox rate is 85%. A week later it's 83%. Then 80%. That's drift, and it's hard to spot without tracking.
Track these metrics weekly. Inbox rate (what percentage land in the inbox folder). Spam folder rate. Bounce rate. Engagement metrics like opens and clicks. Plot them on a simple spreadsheet or your ESP's dashboard. You're looking for trends, not individual spikes.
Establish a baseline first. Before analyzing drift after an update, you need to know what 'normal' looks like for your sending. If your inbox rate is usually 87% with normal variance of plus or minus 2%, then seeing it drop to 82% is meaningful. If you've never measured it, you can't tell what's drift and what's just noise.
Control for your own changes. Did you update your template. Send to a different list segment. Change authentication settings. If so, that's not drift from their update. It's from your change. Document everything you do during the testing period so you can rule it out.
Watch for the timeline. Provider updates usually take 3 to 7 days to fully propagate (they push changes in waves). Algorithmic changes might take 2 to 3 weeks to show their full effect because engagement data has to accumulate. If your numbers are shifting outside that window, something else is happening.
Set up weekly monitoring starting today. You'll catch drift early and be able to respond before it becomes a real problem.
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