# MailerCheck

```json
{
  "name": "MailerCheck",
  "slug": "mailercheck",
  "url": "https://composio.dev/toolkits/mailercheck",
  "markdown_url": "https://composio.dev/toolkits/mailercheck.md",
  "logo_url": "https://logos.composio.dev/api/mailercheck",
  "categories": [
    "advertising & marketing"
  ],
  "is_composio_managed": false,
  "updated_at": "2026-08-20T15:33:03.872Z"
}
```

![MailerCheck logo](https://logos.composio.dev/api/mailercheck)

## Description

Securely connect your AI agents and chatbots (Claude, ChatGPT, Cursor, etc) with MailerCheck MCP or direct API to verify email addresses, validate email lists, review verification results, and monitor account credits through natural language.

## Summary

MailerCheck is an email verification service for checking addresses and lists.
It helps protect sender reputation by reducing bounces and bad contacts.

## Categories

- advertising & marketing

## Toolkit Details

- Tools: 9

## Images

- Logo: https://logos.composio.dev/api/mailercheck

## Authentication

- **Api Key**
  - Type: `api_key`
  - Description: Api Key authentication for MailerCheck.
  - Setup:
    - Configure Api Key credentials for MailerCheck.
    - Use the credentials when creating an auth config in Composio.

## Suggested Prompts

- Verify new signup email addresses
- Check MailerCheck account credit balance
- Review latest list verification results

## Supported Tools

| Tool slug | Name | Description |
|---|---|---|
| `MAILERCHECK_CREATE_VERIFICATION_LIST` | Create Verification List | Create a MailerCheck verification list by ingesting a name and email-address array. Creating a one-address list did not reduce the account credit balance during live probing. This action does not invoke the separate, credit-consuming Start List Verification operation. |
| `MAILERCHECK_DELETE_VERIFICATION_LIST` | Delete Verification List | Permanently and irreversibly delete a MailerCheck verification list by ID. Use only when the caller explicitly intends to remove the list. |
| `MAILERCHECK_GET_CREDIT_BALANCE` | Get Credit Balance | Return the current MailerCheck verification-credit balance. Use this before VERIFY_EMAIL or START_LIST_VERIFICATION when cost matters. |
| `MAILERCHECK_GET_CURRENT_ACCOUNT` | Get Current Account | Return the connected MailerCheck user and account identity. Use this to confirm which user and account the API token represents. |
| `MAILERCHECK_GET_VERIFICATION_LIST` | Get Verification List | Return one verification list, including its status, item count, verification timing, and aggregate result statistics. |
| `MAILERCHECK_LIST_VERIFICATION_LISTS` | List Verification Lists | Return one page of verification lists for the connected MailerCheck account, with an opaque cursor when another provider-controlled page exists. |
| `MAILERCHECK_LIST_VERIFICATION_RESULTS` | List Verification Results | Return one page of email-level results for a verification list, optionally filtered by classification. The success envelope and pagination behavior are based on MailerCheck documentation and were not live-verified because producing results requires a credit-consuming list verification. |
| `MAILERCHECK_START_LIST_VERIFICATION` | Start List Verification | Irreversibly start verification of every address in a MailerCheck list. A successful call spends one verification credit per address. Before calling, use GET_VERIFICATION_LIST to inspect the list count and GET_CREDIT_BALANCE to confirm the current credit_balance. This endpoint was not live-executed because the authorized verification-credit budget was exhausted. |
| `MAILERCHECK_VERIFY_EMAIL` | Verify Email | Consumes exactly one MailerCheck verification credit on every successful call. Synchronously verify one email address and return its classification; check GET_CREDIT_BALANCE first if cost matters. |

## Supported Triggers

None listed.

## Installation and MCP Setup

### Path 1: SDK Installation

#### Path 1, Step 1: Install Composio

Install the Composio SDK
```python
pip install composio_openai
```

```typescript
npm install @composio/openai
```

#### Path 1, Step 2: Initialize Composio and Create Tool Router Session

Import and initialize Composio client, then create a Tool Router session
```python
from openai import OpenAI
from composio import Composio
from composio_openai import OpenAIResponsesProvider

composio = Composio(provider=OpenAIResponsesProvider())
openai = OpenAI()
session = composio.create(user_id='your-user-id')
```

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

const composio = new Composio({
  provider: new OpenAIResponsesProvider(),
});
const openai = new OpenAI({});
const session = await composio.create('your-user-id');
```

#### Path 1, Step 3: Execute MailerCheck Tools via Tool Router with Your Agent

Get tools from Tool Router session and execute MailerCheck actions with your Agent
```python
tools = session.tools
response = openai.responses.create(
  model='gpt-4.1',
  tools=tools,
  input=[{
    'role': 'user',
    'content': 'Verify the email address lead@example.com with MailerCheck and report the status.'
  }]
)
result = composio.provider.handle_tool_calls(
  response=response,
  user_id='your-user-id'
)
print(result)
```

```typescript
const tools = session.tools;
const response = await openai.responses.create({
  model: 'gpt-4.1',
  tools: tools,
  input: [{
    role: 'user',
    content: 'Verify the email address lead@example.com with MailerCheck and report the status.'
  }],
});
const result = await composio.provider.handleToolCalls(
  'your-user-id',
  response.output
);
console.log(result);
```

### Path 2: MCP Server Setup

#### Path 2, Step 1: Install Composio

Install the Composio SDK for Python or TypeScript
```python
pip install composio claude-agent-sdk
```

```typescript
npm install @composio/core ai @ai-sdk/openai @ai-sdk/mcp
```

#### Path 2, Step 2: Initialize Client and Create Tool Router Session

Import and initialize the Composio client, then create a Tool Router session for MailerCheck
```python
from composio import Composio
from claude_agent_sdk import ClaudeSDKClient, ClaudeAgentOptions

composio = Composio(api_key='your-composio-api-key')
session = composio.create(user_id='your-user-id')
url = session.mcp.url
```

```typescript
import { Composio } from '@composio/core';

const composio = new Composio({ apiKey: 'your-api-key' });
const session = await composio.create('your-user-id');
console.log(`Tool Router session created: ${session.mcp.url}`);
```

#### Path 2, Step 3: Connect to AI Agent

Use the MCP server with your AI agent (Anthropic Claude or Mastra)
```python
import asyncio

options = ClaudeAgentOptions(
    permission_mode='bypassPermissions',
    mcp_servers={
        'tool_router': {
            'type': 'http',
            'url': url,
            'headers': {
                'x-api-key': 'your-composio-api-key'
            }
        }
    },
    system_prompt='You are a helpful assistant with access to MailerCheck tools.',
    max_turns=10
)

async def main():
    async with ClaudeSDKClient(options=options) as client:
        await client.query('Check the MailerCheck account credit balance and summarize remaining verification credits.')
        async for message in client.receive_response():
            if hasattr(message, 'content'):
                for block in message.content:
                    if hasattr(block, 'text'):
                        print(block.text)

asyncio.run(main())
```

```typescript
import { openai } from '@ai-sdk/openai';
import { experimental_createMCPClient as createMCPClient } from '@ai-sdk/mcp';
import { generateText } from 'ai';

const client = await createMCPClient({
  transport: {
    type: 'http',
    url: session.mcp.url,
    headers: {
      'x-api-key': 'your-composio-api-key',
    },
  },
});

const tools = await client.tools();
const { text } = await generateText({
  model: openai('gpt-4o'),
  tools,
  messages: [{
    role: 'user',
    content: 'Check the MailerCheck account credit balance and summarize remaining verification credits.'
  }],
  maxSteps: 5,
});

console.log(`Agent: ${text}`);
```

## Why Use Composio?

### 1. AI Native MailerCheck Integration

- Supports both MailerCheck MCP and direct API based integrations
- Structured, LLM-friendly schemas for reliable email verification workflows
- Rich coverage for checking single emails, validating lists, reading reports, and tracking credits

### 2. Managed Auth

- Secure API key handling without hard-coding MailerCheck credentials in your agent code
- Central place to manage, scope, and revoke MailerCheck access
- Per user and per environment credentials for cleaner, safer deployments

### 3. Agent Optimized Design

- Tools are tuned so agents can reliably verify addresses and explain MailerCheck results
- Comprehensive execution logs so you always know which email was checked, when, and on whose behalf
- Works with auth_configs.create(), connected_accounts.link(), and mcp.create() when you need deeper setup control

### 4. Enterprise Grade Security

- Fine-grained RBAC so you control which agents and users can access MailerCheck
- Scoped, least privilege access to MailerCheck verification and credit data
- Full audit trail of agent actions to support review and compliance

## Use MailerCheck with any AI Agent Framework

Choose a framework you want to connect MailerCheck with:

None listed.

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## Frequently Asked Questions

### Do I need my own developer credentials to use MailerCheck with Composio?

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

### Can I use multiple toolkits together?

Yes! Composio's Tool Router enables agents to use multiple toolkits. [Learn more](https://docs.composio.dev/tool-router/overview).

### Is Composio secure?

Composio is SOC 2 and ISO 27001 compliant with all data encrypted in transit and at rest. [Learn more](https://trust.composio.dev).

### What if the API changes?

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

---
[See all toolkits](https://composio.dev/toolkits) · [Composio docs](https://docs.composio.dev/llms.txt)