Understanding catch-all results

A catch-all result is the most misunderstood outcome in email verification. This page explains what it is, why a “successful” probe against one proves nothing, and why we charge for it exactly once.

What is a catch-all domain?

A catch-all (or “accept-all”) domain is configured to accept mail for every address at the domain, whether or not the mailbox exists. Send to anything@example.com and the server says 250 OK — then sorts out (or silently drops) the unknown ones later.

Why a successful probe proves nothing

Our strongest check is a live SMTP conversation: we ask the mail server whether it will accept a given recipient. On a normal domain, a 250 acceptance is a strong signal the mailbox exists. On a catch-all domain, the server accepts everyone — so a 250 tells you only that the domain is catch-all, not that the person’s mailbox is real. That is why we return the verdict risky rather than deliverable.

To detect this, we probe a deliberately random, almost-certainly-nonexistent address alongside the real one. If the server accepts that too, the domain is catch-all. You can see this exact step in the evidence.

What we return

• Verdict risky with reason catch_all.
• A confidence figure where available.
• The full evidence sequence, including the catch-all detection probe and the server’s actual responses.

Why we charge once

Detecting catch-all takes real work — a full SMTP exchange plus the extra detection probe — so it is a billable answer. But it is a single answer about one address, so it is charged once, never doubled for the two probes it took to reach. See How billing works, rule 3.