# Catch-all detection

> How EmailPal detects catch-all domains by probing a mailbox that cannot exist before trusting RCPT TO on your contact. Catch-alls are their own verdict, never a valid you cannot rely on.

Source: https://emailpal.io/help/catch-all-detection

## The probe

Many business domains accept mail to any local part. A verifier that only asks "does jane@company exist?" hears yes for jane, for asdfghjkl, and for your typo. Those later bounce — or worse, sit in a bit bucket nobody reads — after your warmed mailbox has already spent the send.

EmailPal asks about an address that **cannot** be a real mailbox first. If that is accepted, the domain is **catch-all**. Your contact is not confirmed.

No message is sent. `RCPT TO` only. One probe per domain is cached for a day so a large CSV does not hammer the same MX for every row.

[What is a catch-all email?](/help/what-is-a-catch-all-email) is the definition. This page is the mechanism. The six-way result set: [Six verification verdicts](/help/six-verification-verdicts).

## Why other tools call catch-alls valid

SMTP's `RCPT TO` was not designed as a people-directory. On a well-behaved server, a `yes` means the mailbox exists and a `no` means it does not. On a catch-all, both answers are `yes`. A two-state verifier has nowhere to put that and picks valid because valid is the happy path.

EmailPal's six verdicts exist so we do not have to lie. Catch-all is a first-class answer. Unknown is a first-class answer when the server greylists the probe.

This is the same engine on the dashboard, `POST /api/public/v1/verify`, and the `verify_list` MCP tool. [List verification by EmailPal](/help/list-verification-by-emailpal).

## What we do not do

- We do not deliver a message. There is no "confirmation email" to the prospect.
- We do not try 50 random local-parts per domain. One impossible mailbox is enough to learn the policy; we cache it.
- We do not upgrade catch-all to valid because a third-party enrichment API said the person works there. That is a different data source. Use it if you want; do not ask us to relabel SMTP.

## FAQs

### Should I ever mail catch-alls?

That is your risk budget. We will not pretend they are valid. Many teams drop them; some mail a LinkedIn-matched subset at lower volume. On a brand-new or newly claimed mailbox, drop them.

### Can a domain be catch-all for some MX and not others?

We report what the server we reached told us. If results look mixed, the domain may be greylisting probes — verdict **unknown** is the honest answer.

### Why did a real person come back catch-all?

Because we cannot distinguish them from a typo. The domain accepted a mailbox that cannot exist. The person can still be real. SMTP cannot say so.

### Does this slow down a 10,000-row upload?

The expensive part is talking to MX hosts. Caching the per-domain probe is how a list of 200 people at the same company does not become 200 catch-all probes.

## Need More Help?

[How to verify an email list before sending](/help/how-to-verify-an-email-list-before-sending).