Every email verification vendor on the market today will tell you they hit 99% accuracy. Some say 99.9%. A few brave ones say 99.99%. None of them define what they are measuring, and almost none of them publish how they test it. This is the most important number in our entire category, and the industry has collectively agreed not to look at it too closely.
We think that is silly. So this post is the version of the accuracy conversation we wish we had read before we started building CleanMyList.
Accuracy of what, exactly?
There are three different things people mean when they say a verifier is accurate, and they are all measured differently.
- Bounce match rate — given a list, how well does the verifier predict which addresses will actually bounce when you send to them.
- Catch-all coverage — when a domain accepts every address, can the verifier tell you anything useful about it, or does it shrug and say risky.
- Decision stability — if you run the same address through the same verifier twice, an hour apart, do you get the same answer.
Most marketing numbers are bounce match rate, measured against a curated test set that the vendor controls. That is fine for marketing, but it is not how your list looks. Your list has corporate domains, abandoned consumer mailboxes, and a long tail of weird TLDs that the vendor probably did not test.
How we talk about accuracy at CleanMyList
We do not publish an accuracy percentage today because we do not yet have a representative, permissioned set of post-send outcomes to support one. A precise-looking number without that evidence would be marketing, not measurement.
What we do publish in each result is the evidence we actually have: the checks that ran, the warning that shaped the verdict, the score, the checker version, and the time it was checked. When a receiving server will not give us a clear answer, we say risky or unknown instead of claiming certainty.