# Find the addresses that would bounce, before the campaign goes out

Bounces hurt a sending domain. Before a campaign, run each address through contact.verify: it returns invalid when the mail server refuses the mailbox, valid when it accepts it, and unknown when no verifier can tell. Remove the invalid ones and the send never hits them.

HTML page: https://www.routergrowth.com/tools/email-finder/bounce-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 20.6 s for $0.0125. Personal fields are masked. A privacy mailbox listed on a developer platform's site came back invalid on Microsoft 365, so a send to it would be expected to bounce.

| email | status | mx_provider | catch_all |
|---|---|---|---|
| p***@***.com | invalid | Microsoft 365 | None |

## How to do it

1. **Export the send list.** Take the addresses from the CRM or the sheet the campaign will use.
2. **Verify each one.** Run contact.verify on every address, as a batch for a long list.
3. **Remove the invalid ones.** Drop every invalid verdict from the send. Keep unknown on a separate list.
4. **Send, then watch.** Send to the valid rows and track bounces; recheck the unknown rows before the next wave.

## Ask it like this

- Verify the 200 addresses in this CSV and give me back only the ones safe to send. (`contact.verify`)
- Check this list for bounces, then send the intro email only to the valid addresses. (`contact.verify`, `email.send`)

## 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": "alex.rivera@example.com"}'
```

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

## Worth knowing

- **Check close to the send.** Mailboxes close when people leave a company. A list verified months ago can bounce today.
- **Unknown is not a bounce.** Unknown means no verifier could decide, often a catch-all or a slow server. It is free, and worth a second check.
- **It does not send.** The check never delivers a message. Sending is a separate call that you choose to make.

## Questions

### Will this stop every bounce?

No check catches all of them. A mailbox can be valid today and closed tomorrow, and catch-all domains cannot be confirmed.

### What counts as a hard bounce?

A permanent refusal, such as a mailbox that does not exist. An invalid verdict predicts this kind.

### Am I charged for unknown results?

No. Only valid and invalid verdicts are charged.

### Can I run a whole list?

Yes. Run contact.verify as a batch, one run per address, with a total cost cap.

## Related

- [Spot an address someone made up on a real company domain](https://www.routergrowth.com/tools/email-finder/fake-checker.md)
- [Check whether a mailbox accepts mail before you trust it](https://www.routergrowth.com/tools/email-finder/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)