# How to integrate Mails so MCP with Claude Code

```json
{
  "title": "How to integrate Mails so MCP with Claude Code",
  "toolkit": "Mails so",
  "toolkit_slug": "mails_so",
  "framework": "Claude Code",
  "framework_slug": "claude-code",
  "url": "https://composio.dev/toolkits/mails_so/framework/claude-code",
  "markdown_url": "https://composio.dev/toolkits/mails_so/framework/claude-code.md",
  "updated_at": "2026-05-12T10:18:21.496Z"
}
```

## Introduction

Manage your Mails so directly from Claude Code with zero worries about OAuth hassles, API-breaking issues, or reliability and security concerns.
You can do this in two different ways:
- Via [Composio Connect](https://dashboard.composio.dev/login?utm_source=toolkits&utm_medium=framework_template&utm_campaign=claude-code&utm_content=composio_connect&next=%2F~%2Forg%2Fconnect%2Fclients%2Fclaude-code) - Direct and easiest approach
- Via [Composio SDK](https://docs.composio.dev/docs?utm_source=toolkits&utm_medium=framework_template&utm_campaign=claude-code&utm_content=composio_sdk) - Programmatic approach with more control

## Also integrate Mails so with

- [OpenAI Agents SDK](https://composio.dev/toolkits/mails_so/framework/open-ai-agents-sdk)
- [Claude Agent SDK](https://composio.dev/toolkits/mails_so/framework/claude-agents-sdk)
- [Claude Cowork](https://composio.dev/toolkits/mails_so/framework/claude-cowork)
- [Codex](https://composio.dev/toolkits/mails_so/framework/codex)
- [OpenClaw](https://composio.dev/toolkits/mails_so/framework/openclaw)
- [Hermes](https://composio.dev/toolkits/mails_so/framework/hermes-agent)
- [CLI](https://composio.dev/toolkits/mails_so/framework/cli)
- [Google ADK](https://composio.dev/toolkits/mails_so/framework/google-adk)
- [LangChain](https://composio.dev/toolkits/mails_so/framework/langchain)
- [Vercel AI SDK](https://composio.dev/toolkits/mails_so/framework/ai-sdk)
- [Mastra AI](https://composio.dev/toolkits/mails_so/framework/mastra-ai)
- [LlamaIndex](https://composio.dev/toolkits/mails_so/framework/llama-index)
- [CrewAI](https://composio.dev/toolkits/mails_so/framework/crew-ai)

## TL;DR

- Only one MCP URL to connect multiple apps with Claude Code with zero auth hassles.
- Programmatic tool calling allows LLMs to write its code in a remote workbench to handle complex tool chaining. Reduces to-and-fro with LLMs for frequent tool calling.
- Handling Large tool responses out of LLM context to minimize context rot.
- Dynamic just-in-time access to 20,000 tools across 1000+ other Apps for cross-app workflows. It loads the tools you need, so LLMs aren't overwhelmed by tools you don't need.

## Connect Mails so to Claude Code

### Connecting Mails so to Claude Code using Composio
1. Add the Composio MCP to Claude

```bash
claude mcp add --scope user --transport http composio https://connect.composio.dev/mcp
```

## What is Claude Code?

Claude Code is Anthropic's command line developer tool that lets you use Claude directly inside your terminal. Instead of switching between your editor, browser, and chat, you can stay in your project folder and ask Claude to help you build, debug, refactor, and understand code right where you're working.
Key features include:
- Terminal-Native Experience: Work with Claude directly in your command line without switching contexts
- MCP Support: Built-in support for Model Context Protocol servers to extend Claude's capabilities
- Project Context: Claude understands your project structure and can read, write, and modify files
- Interactive Development: Ask questions, debug code, and get help in real-time while coding
- Multi-Platform: Works on macOS, Linux, WSL, and Windows

## What is the Mails so MCP server, and what's possible with it?

The Mails so MCP server is an implementation of the Model Context Protocol that connects your AI agent and assistants like Claude, Cursor, etc directly to your Mails so account. It provides structured and secure access to advanced email validation services, so your agent can perform actions like verifying single emails, running bulk checks, and retrieving validation results on your behalf.
- Single email validation: Instantly check if an individual email address is valid and safe to use before sending important messages.
- Bulk email validation: Submit large lists of email addresses for automated deliverability and quality checks, keeping your contact databases clean.
- Batch results retrieval: Effortlessly fetch detailed validation outcomes for previously submitted bulk jobs, so you can review and act on the results.
- Email list hygiene automation: Use the agent to regularly scan and validate contact lists, reducing bounce rates and improving sender reputation.

## Supported Tools

| Tool slug | Name | Description |
|---|---|---|
| `MAILS_SO_RETRIEVE_BATCH_RESULTS` | Retrieve Batch Results | Tool to retrieve results of a bulk validation job. Use after submitting a batch and you have its ID. |
| `MAILS_SO_VALIDATE_BULK_EMAILS` | Validate Bulk Emails | Tool to validate multiple email addresses in bulk. Use when you need to confirm deliverability of a list of emails at once. |
| `MAILS_SO_VALIDATE_SINGLE_EMAIL` | Validate Single Email | Tool to validate a single email address. Use when you need to check deliverability and quality details before sending an email. |

## Supported Triggers

None listed.

## Creating MCP Server - Stand-alone vs Composio SDK

The Mails so MCP server is an implementation of the Model Context Protocol that connects Claude Code (and other AI assistants like Claude and Cursor) directly to your Mails so account. It provides structured and secure access so Claude can perform Mails so operations on your behalf.
With Composio's managed implementation, you don't have to create your own developer app. For production, if you're building an end product, we recommend using your own credentials. The managed server helps you prototype fast and go from 0-1 faster.

## Step-by-step Guide

### 1. Prerequisites

Before starting, make sure you have:
- Claude Pro, Max, or API billing enabled Anthropic account
- Composio API Key
- A Mails so account
- Basic knowledge of Python or TypeScript

### 1. Install Claude Code

To install Claude Code, use one of the following methods based on your operating system:
```bash
# macOS, Linux, WSL
curl -fsSL https://claude.ai/install.sh | bash

# Windows PowerShell
irm https://claude.ai/install.ps1 | iex

# Windows CMD
curl -fsSL https://claude.ai/install.cmd -o install.cmd && install.cmd && del install.cmd
```

### 2. Set up Claude Code

Open a terminal, go to your project folder, and start Claude Code:
- Claude Code will open in your terminal
- Follow the prompts to sign in with your Anthropic account
- Complete the authentication flow
- Once authenticated, you can start using Claude Code
```bash
cd your-project-folder
claude
```

### 3. Set up environment variables

Create a .env file in your project root with the following variables:
- COMPOSIO_API_KEY authenticates with Composio (get it from [Composio dashboard](https://dashboard.composio.dev/login?utm_source=toolkits&utm_medium=framework_template&utm_campaign=claude-code&utm_content=api_key&next=%2F~%2Forg%2Fconnect%2Fclients%2Fclaude-code))
- USER_ID identifies the user for session management (use any unique identifier)
```bash
COMPOSIO_API_KEY=your_composio_api_key_here
USER_ID=your_user_id_here
```

### 4. Install Composio library

No description provided.
```python
pip install composio-core python-dotenv
```

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

### 5. Generate Composio MCP URL

No description provided.
```python
import os
from composio import Composio
from dotenv import load_dotenv

load_dotenv()

COMPOSIO_API_KEY = os.getenv("COMPOSIO_API_KEY")
USER_ID = os.getenv("USER_ID")

composio_client = Composio(api_key=COMPOSIO_API_KEY)

composio_session = composio_client.create(
    user_id=USER_ID,
    toolkits=["mails_so"],
)

COMPOSIO_MCP_URL = composio_session.mcp.url

print(f"MCP URL: {COMPOSIO_MCP_URL}")
print(f"\nUse this command to add to Claude Code:")
print(f'claude mcp add --transport http mails_so-composio "{COMPOSIO_MCP_URL}" --headers "X-API-Key:{COMPOSIO_API_KEY}"')
```

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

const { COMPOSIO_API_KEY, USER_ID } = process.env;

if (!COMPOSIO_API_KEY || !USER_ID) {
  throw new Error('COMPOSIO_API_KEY and USER_ID required in .env');
}

const composioClient = new Composio({ apiKey: COMPOSIO_API_KEY });

const composioSession = await composioClient.create(USER_ID, {
  toolkits: ['mails_so'],
});

const composioMcpUrl = composioSession?.mcp.url;

console.log(`MCP URL: ${composioMcpUrl}`);
console.log(`\nUse this command to add to Claude Code:`);
console.log(`claude mcp add --transport http mails_so-composio "${composioMcpUrl}" --headers "X-API-Key:${COMPOSIO_API_KEY}"`);
```

### 6. Run the script and copy the MCP URL

No description provided.
```python
python generate_mcp_url.py
```

```typescript
node --loader ts-node/esm generate_mcp_url.ts
# or if using tsx
tsx generate_mcp_url.ts
```

### 7. Add Mails so MCP to Claude Code

In your terminal, add the MCP server using the command from the previous step. The command format is:
- claude mcp add registers a new MCP server with Claude Code
- --transport http specifies that this is an HTTP-based MCP server
- The server name (mails_so-composio) is how you'll reference it
- The URL points to your Composio Tool Router session
- --headers includes your Composio API key for authentication
After running the command, close the current Claude Code session and start a new one for the changes to take effect.
```bash
claude mcp add --transport http mails_so-composio "YOUR_MCP_URL_HERE" --headers "X-API-Key:YOUR_COMPOSIO_API_KEY"

# Then restart Claude Code
exit
claude
```

### 8. Verify the installation

Check that your Mails so MCP server is properly configured.
- This command lists all MCP servers registered with Claude Code
- You should see your mails_so-composio entry in the list
- This confirms that Claude Code can now access Mails so tools
If everything is wired up, you should see your mails_so-composio entry listed:
```bash
claude mcp list
```

### 9. Authenticate Mails so

The first time you try to use Mails so tools, you'll be prompted to authenticate.
- Claude Code will detect that you need to authenticate with Mails so
- It will show you an authentication link
- Open the link in your browser (or copy/paste it)
- Complete the Mails so authorization flow
- Return to the terminal and start using Mails so through Claude Code
Once authenticated, you can ask Claude Code to perform Mails so operations in natural language. For example:
- "Check if this email address is valid"
- "Validate a list of emails before campaign"
- "Download results for last batch validation job"

## Complete Code

```python
import os
from composio import Composio
from dotenv import load_dotenv

load_dotenv()

COMPOSIO_API_KEY = os.getenv("COMPOSIO_API_KEY")
USER_ID = os.getenv("USER_ID")

composio_client = Composio(api_key=COMPOSIO_API_KEY)

composio_session = composio_client.create(
    user_id=USER_ID,
    toolkits=["mails_so"],
)

COMPOSIO_MCP_URL = composio_session.mcp.url

print(f"MCP URL: {COMPOSIO_MCP_URL}")
print(f"\nUse this command to add to Claude Code:")
print(f'claude mcp add --transport http mails_so-composio "{COMPOSIO_MCP_URL}" --headers "X-API-Key:{COMPOSIO_API_KEY}"')
```

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

const { COMPOSIO_API_KEY, USER_ID } = process.env;

if (!COMPOSIO_API_KEY || !USER_ID) {
  throw new Error('COMPOSIO_API_KEY and USER_ID required in .env');
}

const composioClient = new Composio({ apiKey: COMPOSIO_API_KEY });

const composioSession = await composioClient.create(USER_ID, {
  toolkits: ['mails_so'],
});

const composioMcpUrl = composioSession?.mcp.url;

console.log(`MCP URL: ${composioMcpUrl}`);
console.log(`\nUse this command to add to Claude Code:`);
console.log(`claude mcp add --transport http mails_so-composio "${composioMcpUrl}" --headers "X-API-Key:${COMPOSIO_API_KEY}"`);
```

## Conclusion

You've successfully integrated Mails so with Claude Code using Composio's MCP server. Now you can interact with Mails so directly from your terminal using natural language commands.
Key features of this setup:
- Terminal-native experience without switching contexts
- Natural language commands for Mails so operations
- Secure authentication through Composio's managed MCP
- Tool Router for dynamic tool discovery and execution
Next steps:
- Try asking Claude Code to perform various Mails so operations
- Add more toolkits to your Tool Router session for multi-app workflows
- Integrate this setup into your development workflow for increased productivity
You can extend this by adding more toolkits, implementing custom workflows, or building automation scripts that leverage Claude Code's capabilities.

## How to build Mails so MCP Agent with another framework

- [OpenAI Agents SDK](https://composio.dev/toolkits/mails_so/framework/open-ai-agents-sdk)
- [Claude Agent SDK](https://composio.dev/toolkits/mails_so/framework/claude-agents-sdk)
- [Claude Cowork](https://composio.dev/toolkits/mails_so/framework/claude-cowork)
- [Codex](https://composio.dev/toolkits/mails_so/framework/codex)
- [OpenClaw](https://composio.dev/toolkits/mails_so/framework/openclaw)
- [Hermes](https://composio.dev/toolkits/mails_so/framework/hermes-agent)
- [CLI](https://composio.dev/toolkits/mails_so/framework/cli)
- [Google ADK](https://composio.dev/toolkits/mails_so/framework/google-adk)
- [LangChain](https://composio.dev/toolkits/mails_so/framework/langchain)
- [Vercel AI SDK](https://composio.dev/toolkits/mails_so/framework/ai-sdk)
- [Mastra AI](https://composio.dev/toolkits/mails_so/framework/mastra-ai)
- [LlamaIndex](https://composio.dev/toolkits/mails_so/framework/llama-index)
- [CrewAI](https://composio.dev/toolkits/mails_so/framework/crew-ai)

## Related Toolkits

- [Reddit](https://composio.dev/toolkits/reddit) - Reddit is a social news platform with thriving user-driven communities (subreddits). It's the go-to place for discussion, content sharing, and viral marketing.
- [Facebook](https://composio.dev/toolkits/facebook) - Facebook is a social media and advertising platform for businesses and creators. It helps you connect, share, and manage content across your public Facebook Pages.
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- [Active campaign](https://composio.dev/toolkits/active_campaign) - ActiveCampaign is a marketing automation and CRM platform for managing email campaigns, sales pipelines, and customer segmentation. It helps businesses engage customers and drive growth through smart automation and targeted outreach.
- [ActiveTrail](https://composio.dev/toolkits/active_trail) - ActiveTrail is a user-friendly email marketing and automation platform. It helps you reach subscribers and automate campaigns with ease.
- [Ahrefs](https://composio.dev/toolkits/ahrefs) - Ahrefs is an SEO and marketing platform for site audits, keyword research, and competitor insights. It helps you improve search rankings and drive organic traffic.
- [Amcards](https://composio.dev/toolkits/amcards) - AMCards lets you create and mail personalized greeting cards online. Build stronger customer relationships with easy, automated card campaigns.
- [Beamer](https://composio.dev/toolkits/beamer) - Beamer is a news and changelog platform for in-app announcements and feature updates. It helps companies boost user engagement by sharing news where users are most active.
- [Benchmark email](https://composio.dev/toolkits/benchmark_email) - Benchmark Email is a platform for creating, sending, and tracking email campaigns. It's built to help you engage audiences and analyze results—all in one place.
- [Bigmailer](https://composio.dev/toolkits/bigmailer) - BigMailer is an email marketing platform for managing multiple brands with white-labeling and automation. It helps teams streamline campaigns and simplify integration with Amazon SES.
- [Brandfetch](https://composio.dev/toolkits/brandfetch) - Brandfetch is an API that delivers company logos, colors, and visual branding assets. It helps marketers and developers keep brand visuals consistent everywhere.
- [Brevo](https://composio.dev/toolkits/brevo) - Brevo is an all-in-one email and SMS marketing platform for transactional messaging, automation, and CRM. It helps businesses engage customers and streamline communications through powerful campaign tools.
- [Campayn](https://composio.dev/toolkits/campayn) - Campayn is an email marketing platform for creating, sending, and managing campaigns. It helps businesses engage contacts and grow audiences with easy-to-use tools.
- [Cardly](https://composio.dev/toolkits/cardly) - Cardly is a platform for creating and sending personalized direct mail to customers. It helps businesses break through the digital clutter by getting real engagement via physical mailboxes.
- [ClickSend](https://composio.dev/toolkits/clicksend) - ClickSend is a cloud-based SMS and email marketing platform for businesses. It streamlines communication by enabling quick message delivery and contact management.
- [Crustdata](https://composio.dev/toolkits/crustdata) - CrustData is an AI-powered data intelligence platform for real-time company and people data. It helps B2B sales teams, AI SDRs, and investors react to live business signals.
- [Curated](https://composio.dev/toolkits/curated) - Curated is a platform for collecting, curating, and publishing newsletters. It streamlines content aggregation and distribution for creators and teams.
- [Customerio](https://composio.dev/toolkits/customerio) - Customer.io is a customer engagement platform for targeted messaging across email, SMS, and push. Easily automate, segment, and track communications with your audience.
- [Cutt ly](https://composio.dev/toolkits/cutt_ly) - Cutt.ly is a URL shortening service for managing and analyzing links. Streamline your workflows with quick, trackable, and branded short URLs.
- [Demio](https://composio.dev/toolkits/demio) - Demio is webinar software built for marketers, offering both live and automated sessions with interactive features. It helps teams engage audiences and optimize lead generation through detailed analytics.

## Frequently Asked Questions

### What are the differences in Tool Router MCP and Mails so MCP?

With a standalone Mails so MCP server, the agents and LLMs can only access a fixed set of Mails so tools tied to that server. However, with the Composio Tool Router, agents can dynamically load tools from Mails so and many other apps based on the task at hand, all through a single MCP endpoint.

### Can I use Tool Router MCP with Claude Code?

Yes, you can. Claude Code fully supports MCP integration. You get structured tool calling, message history handling, and model orchestration while Tool Router takes care of discovering and serving the right Mails so tools.

### Can I manage the permissions and scopes for Mails so while using Tool Router?

Yes, absolutely. You can configure which Mails so scopes and actions are allowed when connecting your account to Composio. You can also bring your own OAuth credentials or API configuration so you keep full control over what the agent can do.

### How safe is my data with Composio Tool Router?

All sensitive data such as tokens, keys, and configuration is fully encrypted at rest and in transit. Composio is SOC 2 Type 2 compliant and follows strict security practices so your Mails so data and credentials are handled as safely as possible.

---
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