ZeroBounce for Claude

Real-time email validation — MCP connector documentation

Connect Claude to ZeroBounce to validate email addresses in chat using your own ZeroBounce API key and credits. The connector uses OAuth: Claude never sees your API key. You paste it once on ZeroBounce’s connect page; ZeroBounce stores it encrypted and uses it only for your validation requests.

Connector URL (copy this exactly):

https://oauth-mcp.zerobounce.net/mcp

What you need

A ZeroBounce account with credits. Sign up or log in.
Your API key from the ZeroBounce API dashboard.
A Claude plan that supports custom connectors: Free (one custom connector), Pro, Max, Team, or Enterprise. Custom connectors work in Claude on the web, Claude Desktop, Cowork, and the mobile apps.

Get your ZeroBounce API key

Open the ZeroBounce API dashboard and sign in.
Copy your API key.
Confirm you have credits (validation uses 1 credit per email; unknown results are not charged).

Keep the key private. Paste it only on the ZeroBounce connect page that Claude opens — not into Claude settings.

Add the connector in Claude

Leave OAuth Client ID and OAuth Client Secret empty. Claude registers itself automatically. Do not put your ZeroBounce API key in request headers.

Pro, Max, or Free (individual)

In Claude, go to Customize → Connectors.
Click +, then Add custom connector.
Name it something like ZeroBounce (optional).
Paste the connector URL above.
Click Add.
Click Connect. Your browser opens ZeroBounce’s connect page.

Team or Enterprise

Only an Owner or Primary Owner can add the connector for the organization. Members then connect with their own ZeroBounce keys.

Owner

Go to Organization settings → Connectors.
Click Add, hover Custom, choose Web.
Paste https://oauth-mcp.zerobounce.net/mcp.
Click Add. Do not fill advanced OAuth client fields.

Each member

Go to Customize → Connectors.
Find the connector (often labeled Custom).
Click Connect. The browser opens ZeroBounce’s connect page.

Each person uses their own API key. Claude only uses tools and credits for the account that signed in.

Complete ZeroBounce sign-in

On the ZeroBounce page, paste your API key.
Click Connect.
You should return to Claude with the connector connected.

If the key is invalid or has extra spaces, the page shows an error. Copy the key again from the dashboard and retry.

Enable it in a chat

Open a conversation.
Click + (lower left) → Connectors.
Turn ZeroBounce on for that chat.
Ask Claude to validate an address, for example:

"Is test@example.com a valid email?"
"Validate these emails: john@company.com, jane@gmail.com, info@startup.io"
"Which of these should not be mailed: [paste a list]?"
"Validate john@company.com and tell me the SMTP provider, whether it is a free email, and the MX record."

Allow the tool when Claude asks. Prefer Allow always only after you trust the connector in your workflow.

Tools

Tool	What it does	Credits
single_email_validation	One address. Returns status, sub-status, SMTP provider, MX, and enrichment (name, gender, location) when you supply an IP.	1 per call
batch_email_validation	Up to 100 addresses in one call, with a result per address.	1 per address

single_email_validation

Parameter	Type	Required	Description
email	string	Yes	The email address to validate
ip_address	string	No	Only if the person whose mailbox you are checking actually provided it; improves accuracy

batch_email_validation

Parameter	Type	Required	Description
emails	array of strings	Yes	List of email addresses to validate (max 100)

How to read results

Status	Meaning
valid	Safe to send
invalid	Address does not exist or has a syntax error
catch-all	Domain accepts all mail — deliverability uncertain
spamtrap	Known spam trap — do not send
abuse	Frequent spam complainer
do_not_mail	Disposable, role-based, or forwarding address
unknown	Could not be verified (no credit charged)

Troubleshooting

Invalid API key on the connect page

Copy the key again from the API dashboard. Remove spaces before and after.

Out of credits

Add credits or upgrade in your ZeroBounce account, then try again. You do not need to reconnect unless the key changed.

Connector shows as disconnected

Remove it in Customize → Connectors (or Organization settings → Connectors for owners) and add it again. Active use keeps the session alive; unused sessions eventually expire (access lasts up to 30 days, with a longer refresh window).

Connect never opens, or Claude says it cannot reach the server

Use the exact URL https://oauth-mcp.zerobounce.net/mcp (HTTPS, /mcp at the end). Do not use mcp.zerobounce.net for this OAuth connector.

Team member cannot add the URL

Ask an Owner to add the connector first. Then you only click Connect.

You filled Client ID / Secret or put the API key in headers

Remove the connector and add it again with only the URL. Authentication is the ZeroBounce connect page, not Claude’s advanced OAuth fields.

Wrong or extra tools in the chat

Turn off other connectors for that conversation, or disable unused tools in Search and tools.

Privacy and security

Your API key is stored encrypted by ZeroBounce. It is not stored in Claude.
Validation calls go to ZeroBounce using your key and your credits.
Disconnect anytime in Claude (Customize → Connectors). After that, Claude cannot call ZeroBounce until you connect again.
Only add this connector if you intend to validate emails with your ZeroBounce account.

Support

Email support@zerobounce.net or visit the ZeroBounce API documentation.