# What is email verification?

URL: https://email-validation.org/guides/what-is-email-verification/
Updated: 2026-10-20

> Documentation index: https://email-validation.org/llms.txt

Email verification checks whether an address can receive mail, without sending a message to it. A verification
service looks at the address's format, its domain's mail setup and, where the mail server allows it, whether the
mailbox exists, then returns a verdict such as deliverable, undeliverable, risky or unknown.

## How a check works

1. **Syntax.** Is the text a well-formed address (`local-part@domain`)? Malformed input such as `jane@@example` or a
   missing domain fails here, before anything else happens.
2. **Domain and DNS.** Does the domain exist, and does it publish **MX records** that say which servers accept its
   mail? A domain without mail records cannot receive mail.
3. **Mailbox.** The checker connects to the domain's mail server and starts the same conversation a sending server
   would (SMTP), asking whether the server accepts mail for this address. It stops before any message is
   transferred, so nothing is delivered.
4. **Extra signals.** The address is compared with what is known about it: is the domain a throwaway inbox service,
   is the address a shared role inbox such as `info@`, does the domain accept mail for every address (catch-all), or
   is the address linked to spam traps or complaints?

The answer combines these steps. In email-validation.org, every result has a [status, a reason and an action](https://email-validation.org/docs/statuses/),
for example `undeliverable` because of `no_mailbox`, with the action `remove`.

## Verification or validation?

In practice the two words mean the same thing. Some people use "validation" for the format check alone and
"verification" for the full check including the mailbox. On this site both mean the full check.

## What verification can tell you

- The address is malformed, or its domain cannot receive mail.
- The mailbox does not exist, or is full.
- The address belongs to a disposable inbox service or a shared role inbox.
- The domain accepts mail for every address, so the specific mailbox cannot be confirmed.

## What it cannot tell you

- **Whether the person wants your mail.** Consent comes from how you collected the address, and a confirmation
  email (double opt-in) is the only proof that the person controls the mailbox.
- **Whether a catch-all mailbox exists.** Catch-all servers accept every address during a check. See
  [catch-all emails explained](https://email-validation.org/guides/catch-all-emails/).
- **The future.** A deliverable mailbox can be closed next month. Lists decay, so re-check before large sends.
- **Every server, every time.** Some mail servers delay or block checks. Those results come back `unknown`; with
  email-validation.org they are free and often succeed on a second try.

## When to verify

- **At capture:** on sign-up and lead forms, to catch typos while the person is still there. See the
  [sign-up form guide](https://email-validation.org/docs/guides/signup-form-validation/).
- **Before a campaign:** especially for lists that have not been mailed for a while. See
  [how to clean an email list](https://email-validation.org/guides/email-list-cleaning/).
- **On import:** when a list arrives from an event, a partner or an old system.

## Try it

Check a single address with the free [email checker](https://email-validation.org/email-checker/), clean a list with
[bulk verification](https://email-validation.org/bulk-email-verification/), or build it into your product with the
[API](https://email-validation.org/email-verification-api/).