# How to connect mailfloss to Claude

```json
{
  "title": "How to connect mailfloss to Claude",
  "toolkit": "mailfloss",
  "toolkit_slug": "mailfloss",
  "framework": "Claude Cowork",
  "framework_slug": "claude-cowork",
  "url": "https://composio.dev/toolkits/mailfloss/framework/claude-cowork",
  "markdown_url": "https://composio.dev/toolkits/mailfloss/framework/claude-cowork.md",
  "updated_at": "2026-10-24T05:33:40.713Z"
}
```

## 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 mailfloss account to Claude via Composio Connect, enabling it to verify a single customer email address, check a batch of imported contacts, track asynchronous email verification results, 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 mailfloss with

- [ChatGPT](https://composio.dev/toolkits/mailfloss/framework/chatgpt)
- [Hermes](https://composio.dev/toolkits/mailfloss/framework/hermes-agent)
- [Atomic Agent](https://composio.dev/toolkits/mailfloss/framework/atomic-agent)

## Connect mailfloss to Claude Cowork

### Connecting mailfloss 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](https://claude.ai/customize/connectors?modal=add-custom-connector&connectorName=Composio&connectorUrl=https%3A%2F%2Fconnect.composio.dev%2Fmcp)
### Add manually
In Claude Desktop, click Customize in the left sidebar, then select Connectors and click the + icon at the top.
Click Add custom connector and paste in the Composio MCP server URL:

```bash
https://connect.composio.dev/mcp
```

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

The mailfloss MCP server is an implementation of the Model Context Protocol that connects your AI agent and assistants like Claude, Cursor, etc directly to your mailfloss account. It provides structured and secure access to email verification, batch processing, account details, and usage information, so your agent can verify email addresses, process verification batches, track job status and results, and manage stored verification records on your behalf.
- Individual email verification: Have your agent check an email address and return its Mailfloss verification verdict.
- Batch verification workflows: Direct your agent to submit groups of email addresses for verification, monitor processing status, retrieve results, or cancel pending jobs.
- Verification history: Let the agent review past verification jobs, inspect their verdict breakdowns, and filter job history by source or lifecycle status.
- Account and usage insights: Instruct your agent to check the connected API key, view account and organization details, and review verification usage for a selected period.
- Record management: Have your agent permanently erase stored verification records for specified email addresses when they are no longer needed.

## Supported Tools

| Tool slug | Name | Description |
|---|---|---|
| `MAILFLOSS_CANCEL_BATCH_VERIFICATION` | Cancel Batch Verification | Cancel a pending or in-progress batch verification job. This irreversible operation stops remaining work and re-credits unprocessed emails; it is a no-op if the job has already completed. Composio generates an idempotency key when omitted and preserves it for retries within this execution. Reuse a caller-supplied key for the same cancellation across separate calls. |
| `MAILFLOSS_CHECK_API_KEY` | Check API Key | Verify that the connected Mailfloss API key is valid. Uses the connection's Bearer credential and does not accept credentials, request widget tokens, or return signed-proof fields. |
| `MAILFLOSS_CREATE_BATCH_VERIFICATION` | Create Batch Verification | Submit email addresses for asynchronous batch verification and return the job ID. Optionally request a completion webhook instead of polling. This billable action can fail with 402 insufficient_credits. Composio generates an idempotency key when none is supplied, so internal retries reuse the same key and email list. Separate action calls replay the cached response only when the caller reuses that key with identical emails; changing the list fails with 422, while a concurrent same-key request can fail with 409. |
| `MAILFLOSS_ERASE_VERIFICATION_RECORDS` | Erase Verification Records | Permanently erase stored verification records for the supplied email addresses. This destructive data-privacy operation is irreversible; erased records cannot be recovered. Addresses with no stored records are a successful no-op. The body contains only the documented emails array. Composio generates an idempotency key when omitted and preserves it for retries within this execution. |
| `MAILFLOSS_GET_ACCOUNT` | Get Account | Return the authenticated Mailfloss account holder's identity, contact details, security posture, notification preferences, and signup time. This read does not expose API credentials or two-factor secrets. |
| `MAILFLOSS_GET_BATCH_VERIFICATION_RESULTS` | Get Batch Verification Results | Return one cursor-controlled page of stored batch results after organization floss-setting overrides. These statuses and reasons can differ from Verify Email's raw verdict for the same address; fetching stored results is not documented as consuming verification credits. |
| `MAILFLOSS_GET_BATCH_VERIFICATION_STATUS` | Get Batch Verification Status | Read an asynchronous batch verification job's state and available counters. Polling is not documented as consuming verification credits; authentication, policy, not-found, rate-limit, and server responses remain errors rather than job states. |
| `MAILFLOSS_GET_JOB` | Get Verification Job | Return one verification job and its complete verdict breakdown. Results are null until completion and include all per-reason counters when present. |
| `MAILFLOSS_GET_ORGANIZATION` | Get Organization | Return the authenticated Mailfloss organization's plan, credit balances, current-period usage, trial state, account status, and feature entitlements. This is a read-only view and does not expose API or billing credentials. |
| `MAILFLOSS_GET_USAGE_REPORT` | Get Usage Report | Return verification usage for a UTC calendar period, optionally scoped to one ESP connection. Lifetime reports contain only the authoritative total; their range, status counts, and reason counts are null. |
| `MAILFLOSS_LIST_JOBS` | List Verification Jobs | Return one page of the organization's verification-job history, newest first, with optional source and lifecycle filters. Completed jobs include verdict totals; use Get Job for the full per-reason breakdown. |
| `MAILFLOSS_VERIFY_EMAIL` | Verify Email | Verify one email address and return Mailfloss's raw engine verdict without organization floss-setting overrides. passed means safe to send, undeliverable is a hard failure, risky covers role, disposable, bounced, or complained addresses, and unknown includes accept-all addresses and transient SMTP failures. relay and gibberish are annotations and do not alter the verdict. Each successful call consumes one verification credit; a depleted balance fails with 402 insufficient_credits, so do not retry billable failures blindly. |

## Supported Triggers

None listed.

## Troubleshooting

### 1. Why does Claude not use the Composio connector for mailfloss?

The connector can show as connected, but Claude must use it in each mailfloss conversation.
- Click + at the lower left of the chat, or type /.
- Hover Connectors.
- Turn on Composio.
- Ask Claude to connect to mailfloss again.

### 2. Why does Claude show an MCP server error before mailfloss connects?

Claude can show Couldn't reach the MCP server or Authorization with the MCP server failed when you add the connector for mailfloss.
- 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 mailfloss.
- If it fails again, send the error and the ofid_ reference id to support@composio.dev.

### 3. Why does the mailfloss authorization link not work?

The Composio connector is one server. Your mailfloss account connects separately when Claude asks for it.
- If the browser does not open, or the link expires, ask Claude to retry the mailfloss connection.
- Composio creates a fresh mailfloss authorization link.
- Open that link in your browser and finish the mailfloss sign-in.

### 4. Why do mailfloss actions fail after they worked before?

The mailfloss connection can expire or lose permission.
- Ask Claude to inspect the mailfloss connection.
- If the connection is unhealthy, disconnect it when Claude prompts you.
- Reconnect the mailfloss account and retry the action.
- If Claude shows a permission prompt, approve it before Claude changes data in mailfloss.
- If the action still fails with a permission error, check that the connected account has that permission in mailfloss itself.

### 5. How do I switch to a different mailfloss account?

Claude can manage the mailfloss connection for you.
- Ask Claude to disconnect or delete the current mailfloss account.
- Ask Claude to connect mailfloss again.
- Open the new Composio authorization link for mailfloss.
- Sign in with the other mailfloss account in the browser.
- After the account connects, ask Claude to retry the mailfloss task.

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

The connector belongs to your Claude account, so your mailfloss connection works in Claude Web, Desktop, and Cowork.
- In Claude Desktop, open Customize > Connectors.
- Next to Composio, click ⋮ and click Clear cache.
- If mailfloss 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 mailfloss.

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

The mailfloss MCP server connects Claude Web, Desktop, and Cowork to your mailfloss account through Composio. Once connected, Claude can use the available mailfloss tools and triggers to complete tasks on your behalf.

## Complete Code

None listed.

## How to build mailfloss MCP Agent with another framework

- [ChatGPT](https://composio.dev/toolkits/mailfloss/framework/chatgpt)
- [Hermes](https://composio.dev/toolkits/mailfloss/framework/hermes-agent)
- [Atomic Agent](https://composio.dev/toolkits/mailfloss/framework/atomic-agent)

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## Frequently Asked Questions

### What are the differences in Tool Router MCP and mailfloss MCP?

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

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

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 mailfloss tools.

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

Yes, absolutely. You can configure which mailfloss 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 mailfloss data and credentials are handled as safely as possible.

---
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