How do I correlate sending changes with deliverability issues?

Deliverability tanked yesterday. You made some changes recently. maybe a list import, maybe a new campaign, maybe infrastructure tweaks. but which one did it? This is the question that keeps senders up at night. The answer is surprisingly simple: build a timeline.

Document every change you made in the past 2-4 weeks. That includes list uploads or imports, campaign launches, volume increases, content changes, authentication updates, or infrastructure switches. For each one, write down the date and what changed. Don't edit this list later. You want an honest record of what happened when.

Now grab your deliverability metrics from your ESP's reporting dashboard. Pull bounce rates, complaint rates, open rates, and any blocklist alerts. Plot those on the same timeline as your changes. The goal is to see if a metric change follows a sending change.

Here's what correlation actually looks like: You uploaded a list on Tuesday. Bounce rate jumped 15% on Wednesday. That's correlation (though not proof of causation yet). You changed your subject line on Friday. Open rate dropped but bounce rate stayed flat. That's less likely to be your problem. The key is the timing window: most reputation effects show up within 24-72 hours. If your change came weeks before the problem, they're probably unrelated.

Don't stop at finding correlation. Test it. If you think the list upload caused the bounce spike, mark that list as inactive and send a small campaign to your older, proven list. If bounce rates drop, you found your culprit. That's the gold standard of diagnosis.

The real payoff: once you've pinpointed the change, you know exactly what to fix. If it's list quality, clean the list. If it's authentication, fix your records. If it's volume, throttle back. And document your findings so the next time something breaks, you've got a repeatable process to find it fast.