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How to connect Mails so to Claude

Connect Claude Web, Desktop and Cowork to Mails so MCP. Check if this email address is valid, validate a list of emails before campaign, and more using natural language, with authentication handled for you.

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Mails so is an API service for email validation and verification. It helps you keep your contact lists clean, accurate, and free from invalid or risky addresses.

3 Tools

Introduction

Claude is Anthropic's AI assistant, available on the web, in the desktop app, and on mobile. Cowork is its agent for knowledge work, and it runs on all of those surfaces too. Connected to your apps, Claude can work with your files and services to accomplish complex tasks on your behalf.

This guide walks you through the easiest and most secure way to connect your Mails so account to Claude via Composio Connect, enabling it to check if this email address is valid, validate a list of emails before campaign, download results for last batch validation job, and more such actions on your behalf without compromising your account security.

Setup is the same on Claude Web, Desktop, and Cowork, and you only need to do it once. The connector is tied to your account, so it's available in all three.

Also integrate Mails so with

Claude CodeOpenAI Agents SDKClaude Agent SDKCodexOpenClawHermesAtomic AgentGoogle ADKLangChainVercel AI SDKMastra AILlamaIndexCrewAIPydantic AIAutoGen

Connecting Mails so to Claude Web, Desktop, and Cowork

Two ways to add the Composio connector. Pick whichever you prefer.

1. Add with one click

Click the button. Claude opens with the Composio connector filled in. Click Add, then go to step 2.

Add to Claude

Add manually

In Claude Desktop, click Customize in the left sidebar, then select Connectors and click the + icon at the top.

Claude Desktop connectors screen with Add custom connector selected

Click Add custom connector and paste in the Composio MCP server URL:

bash
https://connect.composio.dev/mcp
Add custom connector dialog with Composio MCP server URL

2. Authorize in your browser

Click Connect. You'll be redirected to a browser window where you can authorize Composio to continue.

Composio authorization screen for Claude Web, Desktop, and Cowork

3. Connect your Mails so account

Back in Claude, ask it to connect to Mails so or give it any Mails so-related task.

For example, ask Claude to:

  • "Check if this email address is valid"
  • "Validate a list of emails before campaign"
  • "Download results for last batch validation job"

It will prompt you to authenticate and authorize access.

That's it. Composio's tools are now available in Claude, and your Mails so account is ready to use.

What is the Mails so Claude Connector, 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.

Troubleshooting

1. Why does Claude not use the Composio connector for Mails so?

The connector can show as connected, but Claude must use it in each Mails so conversation.

  • Click + at the lower left of the chat, or type /.
  • Hover Connectors.
  • Turn on Composio.
  • Ask Claude to connect to Mails so again.

2. Why does Claude show an MCP server error before Mails so connects?

Claude can show Couldn't reach the MCP server or Authorization with the MCP server failed when you add the connector for Mails so.

  • Check that the connector URL is https://connect.composio.dev/mcp.
  • Connectors run from Anthropic's cloud, so your device network is usually not the problem.
  • Add the connector again from Customize > Connectors, then ask Claude to connect Mails so.
  • If it fails again, send the error and the ofid_ reference id to support@composio.dev.

3. Why does the Mails so authorization link not work?

The Composio connector is one server. Your Mails so account connects separately when Claude asks for it.

  • If the browser does not open, or the link expires, ask Claude to retry the Mails so connection.
  • Composio creates a fresh Mails so authorization link.
  • Open that link in your browser and finish the Mails so sign-in.

4. Why do Mails so actions fail after they worked before?

The Mails so connection can expire or lose permission.

  • Ask Claude to inspect the Mails so connection.
  • If the connection is unhealthy, disconnect it when Claude prompts you.
  • Reconnect the Mails so account and retry the action.
  • If Claude shows a permission prompt, approve it before Claude changes data in Mails so.
  • If the action still fails with a permission error, check that the connected account has that permission in Mails so itself.

5. How do I switch to a different Mails so account?

Claude can manage the Mails so connection for you.

  • Ask Claude to disconnect or delete the current Mails so account.
  • Ask Claude to connect Mails so again.
  • Open the new Composio authorization link for Mails so.
  • Sign in with the other Mails so account in the browser.
  • After the account connects, ask Claude to retry the Mails so task.

6. Why is my Mails so connection missing in Claude Desktop or on a Team plan?

The connector belongs to your Claude account, so your Mails so connection works in Claude Web, Desktop, and Cowork.

  • In Claude Desktop, open Customize > Connectors.
  • Next to Composio, click ⋮ and click Clear cache.
  • If Mails so tools still do not appear, click ⋮, disconnect, remove the connector, and add it again.
  • On Team or Enterprise, an Owner or Primary Owner must enable the connector before you can connect Mails so.
TOOLS

Supported Tools

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

Retrieve Batch Results

Tool to retrieve results of a bulk validation job.

Validate Bulk Emails

Tool to validate multiple email addresses in bulk.

Validate Single Email

Tool to validate a single email address.

FRAMEWORKS

How to build Mails so MCP Agent with another framework

Claude Code logo

Claude Code

Use Mails so MCP with Claude Code

OpenAI Agents SDK logo

OpenAI Agents SDK

Use Mails so MCP with OpenAI Agents SDK

Claude Agent SDK logo

Claude Agent SDK

Use Mails so MCP with Claude Agent SDK

Codex logo

Codex

Use Mails so MCP with Codex

OpenClaw logo

OpenClaw

Use Mails so MCP with OpenClaw

Hermes logo

Hermes

Use Mails so MCP with Hermes

Atomic Agent logo

Atomic Agent

Use Mails so MCP with Atomic Agent

Google ADK logo

Google ADK

Use Mails so MCP with Google ADK

LangChain logo

LangChain

Use Mails so MCP with LangChain

Vercel AI SDK logo

Vercel AI SDK

Use Mails so MCP with Vercel AI SDK

Mastra AI logo

Mastra AI

Use Mails so MCP with Mastra AI

LlamaIndex logo

LlamaIndex

Use Mails so MCP with LlamaIndex

CrewAI logo

CrewAI

Use Mails so MCP with CrewAI

Pydantic AI logo

Pydantic AI

Use Mails so MCP with Pydantic AI

AutoGen logo

AutoGen

Use Mails so MCP with AutoGen

FAQ

Frequently asked questions

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.

Yes, you can. Claude Cowork 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.

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.

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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