# Spot an address someone made up on a real company domain

A form can look clean while the address is invented: a real company domain with a mailbox that does not exist. contact.verify asks the mail server and returns invalid for those, valid for a real mailbox and unknown when no one can tell. Use the verdict to block, warn or tag the signup.

HTML page: https://www.routergrowth.com/tools/email-finder/fake-checker
Part of: [Email finder tools](https://www.routergrowth.com/tools/email-finder.md)

## The call

[`contact.verify`](https://www.routergrowth.com/catalog/contact.verify): Verify deliverability of a professional email: valid, invalid, or unknown, with catch-all and mail-server details.

Price on this network: $0.002 per verdict. The exact quote is shown before every run.

## What a real run returned

Run on 2026-10-26: 1 records in 15.1 s for $0.0125. Personal fields are masked. A made up role address on a real commerce company's domain: the domain and mail server exist, the mailbox does not, so the verdict is invalid.

| email | status | mx_provider | company |
|---|---|---|---|
| p***@***.com | invalid | Google Workspace | Shopify |

## How to do it

1. **Hook the form.** Call contact.verify when the address is submitted, or on a nightly batch of new signups.
2. **Read the verdict.** invalid means the mailbox does not exist, even if the domain is real.
3. **Pick a rule.** Block invalid, let unknown through with a flag, and accept valid.
4. **Use the company block.** The response names the company behind the domain, a quick check on the signup's claimed employer.

## Ask it like this

- Check yesterday's 300 trial signups and tag the ones with a mailbox that does not exist. (`contact.verify`)
- Flag fake addresses in this lead form export, then enrich the company of each valid one. (`contact.verify`, `company.enrich`)

## Connect

MCP server: `https://api.routergrowth.com/mcp`

```bash
claude mcp add --transport http routergrowth https://api.routergrowth.com/mcp
```

```bash
npm install -g routergrowth && routergrowth setup
routergrowth run -c contact.verify -i '{"email": "jordan.lee@example.com"}'
```

```bash
curl -X POST https://api.routergrowth.com/v1/run \
  -H "Authorization: Bearer $ROUTERGROWTH_API_KEY" \
  -d '{"capability": "contact.verify", "input": {"email": "jordan.lee@example.com"}}'
```

## Worth knowing

- **A real domain is not enough.** The domain here belongs to a large company with working mail. Only the mailbox was invented, and the check caught it.
- **Not a fraud score.** The call checks the mailbox. It does not judge the person, the IP or the intent behind a signup.
- **Catch-all limits.** Some domains accept any address. Those come back unknown or catch-all, and need another signal.

## Questions

### Can it detect disposable addresses?

It reports whether the mailbox accepts mail. It does not keep a list of disposable providers, so add that rule yourself if you need it.

### Does checking slow down signup?

A check took about 15 seconds here when the first verifiers had no answer. Run it after the form is accepted if speed matters.

### Is the address owner notified?

No. No email is sent; the check only asks the mail server.

### What is charged?

Only a valid or invalid verdict. Unknown results are free.

## Related

- [Check whether a mailbox accepts mail before you trust it](https://www.routergrowth.com/tools/email-finder/checker.md)
- [Find the addresses that would bounce, before the campaign goes out](https://www.routergrowth.com/tools/email-finder/bounce-checker.md)
- [Find where to reach a brand from its YouTube channel](https://www.routergrowth.com/tools/email-finder/youtube.md)
- [Read a TikTok brand account's bio, links and contact email](https://www.routergrowth.com/tools/email-finder/tiktok.md)
- [Find the contact details a brand lists on its social profiles](https://www.routergrowth.com/tools/email-finder/social-media.md)
- [Check whether an email address will accept mail before you send](https://www.routergrowth.com/tools/email-finder/verification-tools.md)
- [Turn the LinkedIn profile you are reading into a verified work email](https://www.routergrowth.com/tools/email-finder/linkedin.md)
- [Get the email and links an Instagram brand account shows](https://www.routergrowth.com/tools/email-finder/instagram.md)
- [Get work emails for the people you want at one company](https://www.routergrowth.com/tools/email-finder/company.md)
- [Find someone's work email from their name and where they work](https://www.routergrowth.com/tools/email-finder/by-name.md)
- [Verify one email address in the middle of a conversation](https://www.routergrowth.com/tools/email-finder/address-verification.md)
- [Verify a whole list of emails without uploading it anywhere](https://www.routergrowth.com/tools/email-finder/bulk-verification-software.md)