Mailboxlayer MCP server for AI agents and assistants

Securely connect your AI agents and chatbots (Claude, ChatGPT, Cursor, etc) with Mailboxlayer MCP or direct API to validate email addresses, detect disposable or typo domains, check SMTP deliverability, and enrich emails with quality data through natural language.

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Api Key

Mailboxlayer is a JSON API that validates and verifies email addresses in real time. It helps ensure accurate, deliverable emails and reduces bounce rates for your apps or workflows.

1 Tools

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Type what you want done — sign in and watch it run live in the Tool Router playground.

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TOOLS

Supported Tools

Every Mailboxlayer action and event your agent gets out of the box.

Check Email Validity

Tool to validate a single email address.

SETUP GUIDE

Connect Mailboxlayer MCP Tool with your Agent

1

Install Composio

typescript
npm install @composio/core ai @ai-sdk/mcp @ai-sdk/openai
Install the Composio SDK and your agent framework
2

Create a session with MCP enabled

typescript
import { Composio } from "@composio/core";

const composio = new Composio();
const { mcp } = await composio.create("your-user-id", {
  toolkits: ["mailboxlayer"],
  mcp: true,
});
Create a session scoped to Mailboxlayer and read its MCP URL and headers
3

Connect your agent to the MCP server

typescript
import { createMCPClient } from "@ai-sdk/mcp";
import { openai } from "@ai-sdk/openai";
import { generateText, stepCountIs } from "ai";

const client = await createMCPClient({
  transport: { type: "http", url: mcp.url, headers: mcp.headers },
});

const { text } = await generateText({
  model: openai("gpt-5.6-sol"),
  tools: await client.tools(),
  prompt: "Verify if john.doe@example.com is a valid email address.",
  stopWhen: stepCountIs(10),
});

console.log(text);
await client.close();
Pass the session's MCP URL and headers to your agent and run a Mailboxlayer request
SETUP GUIDE

Connect Mailboxlayer API Tool with your Agent

1

Install Composio

typescript
npm install @composio/core @composio/openai openai
Install the Composio SDK, the OpenAI provider, and the OpenAI SDK
2

Create a Composio session

typescript
import OpenAI from "openai";
import { Composio } from "@composio/core";
import { OpenAIResponsesProvider } from "@composio/openai";

const composio = new Composio({ provider: new OpenAIResponsesProvider() });
const client = new OpenAI();

const session = await composio.create("your-user-id", { toolkits: ["mailboxlayer"] });
const tools = await session.tools();
Initialize Composio with the OpenAI Responses provider and create a session scoped to Mailboxlayer
3

Run Mailboxlayer tools with your agent

typescript
let response = await client.responses.create({
  model: "gpt-5.6-sol",
  tools,
  input: [{ role: "user", content: "Verify if john.doe@example.com is a valid email address." }],
});

while (response.output.some((o) => o.type === "function_call")) {
  const outputs = await composio.provider.handleToolCalls(session, response.output);
  response = await client.responses.create({
    model: "gpt-5.6-sol",
    tools,
    previous_response_id: response.id,
    input: outputs,
  });
}

console.log(response.output_text);
Send a request, execute the Mailboxlayer tool calls through the session, and print the final answer

Why Use Composio?

AI Native Mailboxlayer Integration

  • Supports both Mailboxlayer MCP and direct API based integrations
  • Structured, LLM-friendly schemas for reliable tool execution
  • Rich coverage for real-time email validation and verification

Managed Auth

  • Central place to manage and revoke API keys for Mailboxlayer
  • No more hard-coded credentials—credentials are securely handled for each user
  • Scoped access for different environments and teams

Agent Optimized Design

  • Tools tested on real world email data for consistent validation results
  • Comprehensive logs for every email validation and enrichment attempt

Enterprise Grade Security

  • Fine-grained RBAC controls for Mailboxlayer access
  • Audit trail for every email address checked via agent
  • Least privilege, environment-specific API key access

Rolling this out across your team?

Give your team centralized access control across every framework with Composio’s MCP Gateway.

EXPLORE MCP GATEWAY
FAQ

Frequently asked questions

Yes, Mailboxlayer requires you to configure your own API key credentials. Once set up, Composio handles secure credential storage and API request handling for you.

Yes! Composio's Tool Router enables agents to use multiple toolkits. Learn more.

Yes. Composio is SOC 2 Type II compliant and is built to keep your Mailboxlayer connection and credentials secure. OAuth tokens and API keys are encrypted, and sensitive customer data is protected at rest and in transit.

Composio also undergoes independent security testing and continuously monitors its systems for security threats. You can review the latest reports and policies in the Composio Trust Center.

Composio maintains and updates all toolkit integrations automatically, so your agents always work with the latest API versions.

Create the key in your Mailboxlayer account settings, then paste it once on Composio's connection page. Composio stores it encrypted and uses it only for the Mailboxlayer actions your agent runs. Nobody else in your workspace can read it, and you can revoke it inside Mailboxlayer at any time.

When you connect a Mailboxlayer account through Composio, every action runs under that account, so anything the agent creates, sends, or changes shows up in Mailboxlayer as done by you. Keep an approval step in your prompt for actions with side effects, such as sending or deleting, and have the agent draft first.

Whatever the credentials you connect allow inside Mailboxlayer. If Mailboxlayer lets you scope a key to specific permissions, create a scoped one so the agent can only do what you intend. You can revoke the key inside Mailboxlayer at any time.

Yes. Composio supports multiple connected accounts for the same app, and that works in Claude, ChatGPT, or any other assistant you connect through Composio. Give each Mailboxlayer connection a name such as work or personal, and the assistant uses the one you mention in the request. Each account keeps its own credentials and nothing is merged.

The connection stops working the moment Mailboxlayer rejects the old key. Create a new key in Mailboxlayer and reconnect the account from the Composio dashboard or by asking your agent to reconnect Mailboxlayer. Nothing else changes.

Composio's free Hobby plan includes 100,000 tool calls per month with no credit card, which covers most personal Mailboxlayer use. Paid plans add higher limits and team features. Your Mailboxlayer plan and its API limits still apply as usual.

Built-in connectors usually give one AI access to a limited set of apps. Many people use Composio because it lets their AI connect to more apps than it normally supports, or connect to multiple accounts for the same app (e.g. connect Claude to multiple Mailboxlayer accounts).

With Composio, you connect Mailboxlayer once and then use it across different AI assistants without setting it up separately in each one. Connect your apps to Composio once, then connect Composio to whichever AI you use, whether that's Claude, ChatGPT, Hermes, or your own custom assistant.

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