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How to connect SMTPing to Claude

Connect Claude Web, Desktop and Cowork to SMTPing MCP. Verify an email address before sending, check an address against threat lists, and more using natural language, with authentication handled for you.

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SMTPing is an email verification service for validating addresses, checking threat lists, and monitoring account usage. It helps teams reduce bounced emails and protect sender reputation.

14 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 SMTPing account to Claude via Composio Connect, enabling it to verify an email address before sending, check an address against threat lists, review SMTPing credits and API usage, 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 SMTPing with

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Connecting SMTPing 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 SMTPing account

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

For example, ask Claude to:

  • "Verify an email address before sending"
  • "Check an address against threat lists"
  • "Review SMTPing credits and API usage"

It will prompt you to authenticate and authorize access.

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

What is the SMTPing Claude Connector, and what's possible with it?

The SMTPing MCP server is an implementation of the Model Context Protocol that connects your AI agent and assistants like Claude, Cursor, etc directly to your SMTPing account. It provides structured and secure access to email verification, threat-list checks, bulk jobs, credits, and usage data, so your agent can verify addresses, identify risky emails, process large lists, monitor credits, and review API usage on your behalf.

  • Email address verification: Have your agent verify individual email addresses and review their deliverability status and domain flags.
  • Threat-list screening: Direct your agent to check an email or a batch of up to 1,000 addresses against a selected SMTPing threat list.
  • Bulk email processing: Instruct your agent to start large verification or threat-list jobs for up to 100,000 addresses, then check progress and retrieve the results.
  • Risk and domain flag checks: Let the agent inspect all six SMTPing risk and domain flags for a specific email address.
  • Credits and usage tracking: Have your agent check remaining credits, review aggregate usage, list recent API requests, or export usage history as a CSV file.

Troubleshooting

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

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

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

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

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

  • 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 SMTPing.
  • If it fails again, send the error and the ofid_ reference id to support@composio.dev.

3. Why does the SMTPing authorization link not work?

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

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

4. Why do SMTPing actions fail after they worked before?

The SMTPing connection can expire or lose permission.

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

5. How do I switch to a different SMTPing account?

Claude can manage the SMTPing connection for you.

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

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

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

  • In Claude Desktop, open Customize > Connectors.
  • Next to Composio, click ⋮ and click Clear cache.
  • If SMTPing 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 SMTPing.
TOOLS

Supported Tools

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

Check Email

Check one email address against one selected SMTPing threat list and report whether it matched.

Check Email Batch

Synchronously check 1 to 1,000 email addresses against one selected SMTPing threat list and return all results.

Check Email Flags

Return all six SMTPing risk and domain flags for one email address in one request.

Create Bulk Check Job

Start an asynchronous SMTPing threat-list check for 1 to 100,000 email addresses.

Create Bulk Verification Job

Start asynchronous verification for 1 to 100,000 email addresses and return the job ID to use for status polling and result retrieval.

Export Usage

Download SMTPing usage history as a CSV file for the provider's default date range.

Get Bulk Check Job

Get progress and match counts for an asynchronous threat-list check job.

Get Bulk Check Results

Return all address-level matches for a bulk threat-list check job after its status is Succeeded or Completed.

Get Bulk Verification Job

Get progress and summary counts for an asynchronous bulk verification job.

Get Bulk Verification Results

Return all address-level results for a bulk verification job after its status is Succeeded.

Get Credits

Return the connected account's current credit balance, plan, and daily remaining credits.

Get Usage

Return aggregate request, email, credit, status, endpoint, and error usage for SMTPing's current default date range.

List Usage Requests

Return the newest available page of individual SMTPing API request history, up to the provider default of 50 rows, with page metadata.

Verify Email

Verify one email address and return its deliverability status and domain flags.

FRAMEWORKS

How to build SMTPing MCP Agent with another framework

ChatGPT logo

ChatGPT

Use SMTPing MCP with ChatGPT

Hermes logo

Hermes

Use SMTPing MCP with Hermes

Atomic Agent logo

Atomic Agent

Use SMTPing MCP with Atomic Agent

FAQ

Frequently asked questions

With a standalone SMTPing MCP server, the agents and LLMs can only access a fixed set of SMTPing tools tied to that server. However, with the Composio Tool Router, agents can dynamically load tools from SMTPing 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 SMTPing tools.

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

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