What actually differs between verification tools

1. The verdict model

Every tool sorts an address into buckets, but the buckets are not the same everywhere. ClearMX uses four, and publishes the reason behind each one.

Deliverable

The mail server accepted the exact mailbox on a domain that is not a catch-all. This is the only state that means what people assume it means.

Risky

The address resolves, but something lowers confidence — a catch-all domain, a role address like info@, or a throwaway provider. It may well arrive; it is your call whether to send.

Undeliverable

Mail will bounce: no MX record, the server said the mailbox does not exist, or the address is not valid syntax.

Unknown

The probe was inconclusive — greylisted, timed out, or refused. Not a verdict dressed up as one.

2. What happens when the answer is not knowable

This is the real difference. Catch-all domains accept every address at the door, and some providers block mailbox probes outright. A tool can either return "deliverable" anyway, or admit it does not know. ClearMX caps any address without a confirmed mailbox below its deliverable threshold, so the classifier mechanically cannot call it deliverable. A tool that never returns unknown has not solved that problem; it has hidden it, and decided on your behalf without saying so.

3. Reason codes and explainability

Ask whether you can see why. ClearMX returns a verdict, a 0–100 score and a plain reason for every address, in the dashboard and in the API response, so a send/suppress/review decision can be made without opening documentation. Read the full method on the methodology page.

Methodology

Every check ClearMX runs, and what each one proves.

4. How the checks reach the mailbox

Ask any vendor a direct question: do you send mail to the addresses I am verifying? ClearMX does not — the SMTP probe opens a conversation with the mail server and stops before anything is delivered. Nobody on your list receives anything.

5. Privacy and retention

Where does verification run, what is stored, and can you delete it? ClearMX runs on EU-hosted infrastructure, never persists an anonymous free-tool lookup, and lets you delete an import when the engagement ends.

6. Billing model

Per-credit or per-seat? Do credits expire? ClearMX sells credits that never expire; buying them does not require a subscription, and the optional monthly plan is a discount on the same credits, not a different product.

Pricing

Every published rate, and the calculator that produces them.

7. When another tool is the better choice

There are several, and pretending otherwise would make this page useless. Pick a different tool when you need out-of-the-box connectors into a specific ESP or CRM and do not want to wire an API; when your procurement needs compliance paperwork a two-person company cannot hand you today; when you want one vendor doing verification and sending and list management together; or when your volume is high enough that a negotiated enterprise contract beats published per-credit pricing.

8. What to ask for in a pilot

Run the same thousand addresses through both tools. Compare how many land in each bucket, not just the deliverable count. Open the disagreements and read both reason codes. Confirm no mail was sent to anyone on the list. Then check what each tool did with your catch-all domains, because that is where the two answers will differ most.