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How to connect Mailersend to Claude

Connect Claude Web, Desktop and Cowork to Mailersend MCP. Add a new sending domain for your app, list all smtp users for our domain, and more using natural language, with authentication handled for you.

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MailerSend is a transactional email platform for developers to send, receive, and track emails via API. It provides reliable deliverability, analytics, and easy integration for your apps.

23 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 Mailersend account to Claude via Composio Connect, enabling it to add a new sending domain for your app, list all SMTP users for our domain, check current API quota 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 Mailersend with

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

Connecting Mailersend 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 Mailersend account

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

For example, ask Claude to:

  • "Add a new sending domain for your app"
  • "List all SMTP users for our domain"
  • "Check current API quota usage"

It will prompt you to authenticate and authorize access.

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

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

The Mailersend MCP server is an implementation of the Model Context Protocol that connects your AI agent and assistants like Claude, Cursor, etc directly to your Mailersend account. It provides structured and secure access to your transactional email infrastructure, so your agent can perform actions like sending emails, managing domains, configuring webhooks, and monitoring API usage on your behalf.

  • Seamless domain management: Register new sending domains, verify their status, and retrieve detailed configuration information to ensure reliable email delivery.
  • Automated email and SMTP user setup: Quickly create SMTP users and API tokens as needed for secure and scalable application integration.
  • Webhook configuration and event tracking: Set up and delete webhooks to monitor real-time email events such as sent, delivered, or opened messages, enabling proactive workflows and notifications.
  • Recipient and quota insights: List recipients for specific domains and monitor your API usage to stay within account limits and optimize deliverability.
  • Centralized resource discovery: Retrieve general API resources and overview endpoints to streamline Mailersend integration and administration directly from your agent.

Troubleshooting

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

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

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

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

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

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

3. Why does the Mailersend authorization link not work?

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

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

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

The Mailersend connection can expire or lose permission.

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

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

Claude can manage the Mailersend connection for you.

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

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

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

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

Supported Tools

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

Create Sending Domain

Tool to add a new sending domain to MailerSend.

Create SMTP User

Tool to create a new SMTP user.

Create API Token

Creates a new API token with specified scopes (permissions) for a domain.

Create Webhook

Tool to create a new webhook for a MailerSend domain.

Delete Webhook

Tool to delete an existing webhook.

Get API Quota

Tool to retrieve current API usage quota.

Get Domain

Tool to retrieve detailed information about a specific sending domain in MailerSend.

List Domain Recipients

Tool to list recipients for a domain.

Get sending domains

Retrieve a paginated list of all sending domains configured in your MailerSend account.

Get general API resources

Tool to retrieve general API resources and information.

List Sender Identities

Retrieves a paginated list of sender identities configured in your MailerSend account.

Get sent messages

Tool to retrieve a paginated list of sent messages.

Get email recipients

Tool to retrieve a list of email recipients.

Get SMS Activity

Tool to retrieve SMS activity logs.

Get SMS Inbounds

Retrieve inbound SMS route configurations.

List SMS Messages

Retrieves a paginated list of SMS messages sent through the MailerSend API.

Get SMS Numbers

Tool to retrieve a paginated list of SMS phone numbers.

Get SMS recipients

Tool to retrieve a list of SMS recipients.

Get SMTP users

Tool to retrieve a list of SMTP users.

Get email templates

Retrieves a paginated list of email templates from your MailerSend account.

Get API Tokens

Retrieves a paginated list of API tokens associated with your MailerSend account.

Get users

Tool to retrieve a list of users associated with your account.

List webhooks

Tool to retrieve a list of webhooks.

FRAMEWORKS

How to build Mailersend MCP Agent with another framework

Claude Code logo

Claude Code

Use Mailersend MCP with Claude Code

OpenAI Agents SDK logo

OpenAI Agents SDK

Use Mailersend MCP with OpenAI Agents SDK

Claude Agent SDK logo

Claude Agent SDK

Use Mailersend MCP with Claude Agent SDK

Codex logo

Codex

Use Mailersend MCP with Codex

OpenClaw logo

OpenClaw

Use Mailersend MCP with OpenClaw

Hermes logo

Hermes

Use Mailersend MCP with Hermes

Atomic Agent logo

Atomic Agent

Use Mailersend MCP with Atomic Agent

Google ADK logo

Google ADK

Use Mailersend MCP with Google ADK

LangChain logo

LangChain

Use Mailersend MCP with LangChain

Vercel AI SDK logo

Vercel AI SDK

Use Mailersend MCP with Vercel AI SDK

Mastra AI logo

Mastra AI

Use Mailersend MCP with Mastra AI

LlamaIndex logo

LlamaIndex

Use Mailersend MCP with LlamaIndex

CrewAI logo

CrewAI

Use Mailersend MCP with CrewAI

Pydantic AI logo

Pydantic AI

Use Mailersend MCP with Pydantic AI

AutoGen logo

AutoGen

Use Mailersend MCP with AutoGen

FAQ

Frequently asked questions

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

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

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