Why Two Email Verifiers Give Different Results on the Same List, and Which to Trust

Two email verifiers disagree on the same list because they handle the hard cases differently: catch-all domains, servers that defer or refuse the check, and addresses that could not be confirmed. Neither tool is lying. They are making different calls on rows where the mail server did not give a clear answer.

The six reasons

Reason	What differs
Unconfirmed addresses	One tool labels them valid, another risky or unknown
Catch-all domains	Valid, risky or its own category; see what is a catch-all domain
Deferred or refused checks	Some retry, some give up, some count a deferral as a pass
Timing	A mailbox can be created or closed between two runs; see how often to verify
Checking server's reputation	Some servers refuse a source they do not know, and each tool checks from its own addresses
Disposable and role lists	Each tool keeps its own lists

The first line is the one that moves the headline number most.

What SimpleVerifier does

SimpleVerifier's rule is that anything the mailbox probe could not confirm is returned as risky, never as valid. Each row carries a status (valid, risky or invalid), a send advice and a reason. The columns are explained in how to read a verification report, and server would not confirm covers the retry group.

A tool that follows the opposite rule shows a larger valid count. That count is not wrong on the day, but it is the one that turns into bounces.

A bigger valid count is not a better result

If one tool says 9,000 of 10,000 are valid and another says 7,500, the first may simply have put 1,500 unconfirmed rows in the valid pile. What matters is how many of the valid group bounce.

How to settle it

1. Run the same sample through both. Bench test email verifiers fairly gives a protocol.
2. List the rows where they disagree.
3. Take 100 to 200 addresses each tool called valid, from the rows where they differ if you can.
4. Send from a warmed inbox, not your main domain.
5. Count hard bounces after a couple of days. Calculate your email bounce rate shows how to read it.

The tool with fewer bounces in its valid group made the better call for your list.

What to do with the disagreeing rows

Treat a row as risky if either tool does. Send the rows both call valid first, and put the rest in a small second batch.

Next step

Run 100 free checks on a sample you have already run elsewhere, with a Google sign-in and no card, and compare the rows. See pricing: Starter is $9 a month for 2,500 emails, one-time packs start at $15 for 10,000 checks, and Pro is $39 a month.