Mailbox verification

The rule

An address is delivered only if the mail server that would receive it confirms it will accept mail for that mailbox. Every delivered row carries the verdict that cleared it, in the email_status column.

Anything else is not delivered and not charged. There is no probably-fine tier, because a bounced send costs you deliverability that is worth more than the row.

Accept-all domains are excluded, not shipped

Some mail servers accept anything addressed to their domain and sort it out later. On those domains, a positive response proves nothing — the mailbox may not exist at all.

Vendors commonly count these as valid, because it inflates the delivered count at no cost to them. We exclude them. It means our files are smaller than they could be, and it is the main reason a LeadProof row behaves the way the label says.

Which address we pick

We read the business's own website, contact and about pages first, and rank what we find. Addresses on the business's own domain outrank anything else on the page. Published role inboxes — info, contact, office, hello, front desk — are preferred, because that is what a business puts on its site for people who want to reach it.

• We deliver the business's published contact address, not a named individual's direct line or personal inbox. If your outreach depends on reaching a specific person by name, this is the wrong product. Observed 2026-08-02.

A failure we shipped, and the rule that came out of it

This is published rather than buried because a methodology page listing only successes tells you nothing about how the operation behaves when it is wrong.

• On 2026-07-23 a font foundry's address was delivered as a lead, because it appeared in the markup of the business's own website. Web-vendor domains — font foundries, site builders, CDNs, agencies — are now excluded by rule, and the exclusion has unit tests. The general class of failure (an address on a page that does not belong to the business) is one we actively hunt rather than consider closed. Observed 2026-07-23.

What a verified mailbox does not tell you

That the address accepts mail. Not that anyone reads it, not that the business wants to hear from you, and not that your offer is relevant. Verification is a deliverability guarantee, and deliberately nothing more.

• A LeadProof list says a business exists, is reachable, and matches your filters. It does not say the business is shopping, hiring, or dissatisfied with its current supplier. We sell no intent signal and no technographic data, and any page implying otherwise is wrong. Observed 2026-08-02.

Questions

Do you deliver accept-all or risky addresses?

No. Only addresses the receiving server confirms as deliverable are delivered, and only those are charged.

What is in the email_status column?

The verdict that cleared the address for delivery, so you can see on what basis each row shipped.

Are these personal email addresses?

No. They are the business's published contact addresses — typically a role inbox on the company's own domain.

Will these addresses bounce?

Every one was confirmed deliverable at build time. Mailboxes can be retired later, which is an argument for sending soon after delivery rather than storing the file.