# 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": "2026-10-04T15:01:29.166Z"
}
```

![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, the OpenAI provider, and the OpenAI SDK
```python
pip install composio composio_openai openai
```

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

#### Path 1, Step 2: Create a Composio session

Initialize Composio with the OpenAI Responses provider and create a session scoped to MailerCheck
```python
import json
from openai import OpenAI
from composio import Composio
from composio_openai import OpenAIResponsesProvider

composio = Composio(provider=OpenAIResponsesProvider())
client = OpenAI()

session = composio.create(user_id="your-user-id", toolkits=["mailercheck"])
tools = session.tools()
```

```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: ["mailercheck"] });
const tools = await session.tools();
```

#### Path 1, Step 3: Run MailerCheck tools with your agent

Send a request, execute the MailerCheck tool calls through the session, and print the final answer
```python
response = client.responses.create(
    model="gpt-5.6-sol",
    tools=tools,
    input=[{"role": "user", "content": "Verify the email address lead@example.com with MailerCheck and report the status."}],
)

while True:
    tool_calls = [o for o in response.output if o.type == "function_call"]
    if not tool_calls:
        break
    results = composio.provider.handle_tool_calls(response=response, session=session)
    response = client.responses.create(
        model="gpt-5.6-sol",
        tools=tools,
        previous_response_id=response.id,
        input=[
            {"type": "function_call_output", "call_id": call.call_id, "output": json.dumps(results[i])}
            for i, call in enumerate(tool_calls)
        ],
    )

print(response.output_text)
```

```typescript
let response = await client.responses.create({
  model: "gpt-5.6-sol",
  tools,
  input: [{ role: "user", content: "Verify the email address lead@example.com with MailerCheck and report the status." }],
});

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);
```

### Path 2: MCP Server Setup

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

Install the Composio SDK and your agent framework
```python
pip install composio claude-agent-sdk
```

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

#### Path 2, Step 2: Create a session with MCP enabled

Create a session scoped to MailerCheck and read its MCP URL and headers
```python
from composio import Composio

composio = Composio()
session = composio.create(user_id="your-user-id", toolkits=["mailercheck"], mcp=True)
```

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

const composio = new Composio();
const { mcp } = await composio.create("your-user-id", {
  toolkits: ["mailercheck"],
  mcp: true,
});
```

#### Path 2, Step 3: Connect your agent to the MCP server

Pass the session's MCP URL and headers to your agent and run a MailerCheck request
```python
import asyncio
from claude_agent_sdk import ClaudeSDKClient, ClaudeAgentOptions, AssistantMessage, TextBlock

options = ClaudeAgentOptions(
    mcp_servers={
        "composio": {
            "type": "http",
            "url": session.mcp.url,
            "headers": session.mcp.headers,
        }
    },
    system_prompt="You are a helpful assistant with access to MailerCheck tools.",
    tools=[],
    allowed_tools=["mcp__composio__*"],
)

async def main():
    async with ClaudeSDKClient(options=options) as client:
        await client.query("Verify the email address lead@example.com with MailerCheck and report the status.")
        async for message in client.receive_response():
            if isinstance(message, AssistantMessage):
                for block in message.content:
                    if isinstance(block, TextBlock):
                        print(block.text)

asyncio.run(main())
```

```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 the email address lead@example.com with MailerCheck and report the status.",
  stopWhen: stepCountIs(10),
});

console.log(text);
await client.close();
```

## 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)