How to integrate Smtp2go MCP with Mastra AI

This guide walks you through connecting Smtp2go to Mastra AI using the Composio tool router. By the end, you'll have a working Smtp2go agent that can search for bounced emails this week, add marketing@mydomain.com as allowed sender, list all verified sender domains through natural language commands. This guide will help you understand how to give your Mastra AI agent real control over a Smtp2go account through Composio's Smtp2go MCP server. Before we dive in, let's take a quick look at the key ideas and tools involved.

Get started for free Get a demo

Smtp2go

Api Key

Smtp2go is a dependable email delivery service that ensures your messages are sent and received reliably. It's designed to give your business fast, secure, and hassle-free transactional email delivery.

32 Tools

Managed auth

Connect Smtp2go without auth hassles

We manage OAuth, API keys, token refresh, and scopes — you just build.

Try for free

Introduction

This guide will help you understand how to give your Mastra AI agent real control over a Smtp2go account through Composio's Smtp2go MCP server.

Before we dive in, let's take a quick look at the key ideas and tools involved.

Also integrate Smtp2go with

OpenAI Agents SDK Claude Agent SDK Claude Code Claude Cowork Codex OpenClaw Hermes CLI Google ADK LangChain Vercel AI SDK LlamaIndex CrewAI

TL;DR

Here's what you'll learn:

Set up your environment so Mastra, OpenAI, and Composio work together
Create a Tool Router session in Composio that exposes Smtp2go tools
Connect Mastra's MCP client to the Composio generated MCP URL
Fetch Smtp2go tool definitions and attach them as a toolset
Build a Mastra agent that can reason, call tools, and return structured results
Run an interactive CLI where you can chat with your Smtp2go agent

What is Mastra AI?

Mastra AI is a TypeScript framework for building AI agents with tool support. It provides a clean API for creating agents that can use external services through MCP.

Key features include:

MCP Client: Built-in support for Model Context Protocol servers
Toolsets: Organize tools into logical groups
Step Callbacks: Monitor and debug agent execution
OpenAI Integration: Works with OpenAI models via @ai-sdk/openai

What is the Smtp2go MCP server, and what's possible with it?

The Smtp2go MCP server is an implementation of the Model Context Protocol that connects your AI agent and assistants like Claude, Cursor, etc directly to your Smtp2go account. It provides structured and secure access to your email sending and management infrastructure, so your agent can perform actions like searching email activity, managing allowed senders, updating sender domains, and controlling IP allow lists on your behalf.

Comprehensive email activity search: Ask your agent to filter and retrieve email events such as sends, opens, clicks, and bounces by recipient, date, or message ID.
Allowed sender management: Have your agent add, update, remove, or view allowed sender email addresses to control who can send emails from your account.
Sender domain configuration: Let the agent register new sender domains for SPF/DKIM verification and manage domain-related settings seamlessly.
IP allow list control: Direct your agent to add or remove IP addresses or CIDR ranges in your account’s IP allow list, enhancing security for sending sources.
Email delivery monitoring: Enable your agent to search and analyze sent emails, helping you monitor delivery, troubleshoot issues, and ensure reliable communication.

What is the Composio tool router, and how does it fit here?

What is Composio SDK?

Composio's Composio SDK helps agents find the right tools for a task at runtime. You can plug in multiple toolkits (like Gmail, HubSpot, and GitHub), and the agent will identify the relevant app and action to complete multi-step workflows. This can reduce token usage and improve the reliability of tool calls. Read more here: Getting started with Composio SDK

The tool router generates a secure MCP URL that your agents can access to perform actions.

How the Composio SDK works

The Composio SDK follows a three-phase workflow:

Discovery: Searches for tools matching your task and returns relevant toolkits with their details.
Authentication: Checks for active connections. If missing, creates an auth config and returns a connection URL via Auth Link.
Execution: Executes the action using the authenticated connection.

Step-by-step Guide

Step by step09 STEPS

Prerequisites

Before starting, make sure you have:

Node.js 18 or higher
A Composio account with an active API key
An OpenAI API key
Basic familiarity with TypeScript

Getting API Keys for OpenAI and Composio

OpenAI API Key

Go to the OpenAI dashboard and create an API key.
You need credits or a connected billing setup to use the models.
Store the key somewhere safe.

Composio API Key

Log in to the Composio dashboard.
Go to Settings and copy your API key.
This key lets your Mastra agent talk to Composio and reach Smtp2go through MCP.

Install dependencies

bash

npm install @composio/core @mastra/core @mastra/mcp @ai-sdk/openai dotenv

Install the required packages.

What's happening:

@composio/core is the Composio SDK for creating MCP sessions
@mastra/core provides the Agent class
@mastra/mcp is Mastra's MCP client
@ai-sdk/openai is the model wrapper for OpenAI
dotenv loads environment variables from .env

Set up environment variables

bash

COMPOSIO_API_KEY=your_composio_api_key_here
COMPOSIO_USER_ID=your_user_id_here
OPENAI_API_KEY=your_openai_api_key_here

Create a .env file in your project root.

What's happening:

COMPOSIO_API_KEY authenticates your requests to Composio
COMPOSIO_USER_ID tells Composio which user this session belongs to
OPENAI_API_KEY lets the Mastra agent call OpenAI models

Import libraries and validate environment

typescript

import "dotenv/config";
import { openai } from "@ai-sdk/openai";
import { Agent } from "@mastra/core/agent";
import { MCPClient } from "@mastra/mcp";
import { Composio } from "@composio/core";
import * as readline from "readline";

import type { AiMessageType } from "@mastra/core/agent";

const openaiAPIKey = process.env.OPENAI_API_KEY;
const composioAPIKey = process.env.COMPOSIO_API_KEY;
const composioUserID = process.env.COMPOSIO_USER_ID;

if (!openaiAPIKey) throw new Error("OPENAI_API_KEY is not set");
if (!composioAPIKey) throw new Error("COMPOSIO_API_KEY is not set");
if (!composioUserID) throw new Error("COMPOSIO_USER_ID is not set");

const composio = new Composio({
  apiKey: composioAPIKey as string,
});

What's happening:

dotenv/config auto loads your .env so process.env.* is available
openai gives you a Mastra compatible model wrapper
Agent is the Mastra agent that will call tools and produce answers
MCPClient connects Mastra to your Composio MCP server
Composio is used to create a Tool Router session

Create a Tool Router session for Smtp2go

typescript

async function main() {
  const session = await composio.create(
    composioUserID as string,
    {
      toolkits: ["smtp2go"],
    },
  );

  const composioMCPUrl = session.mcp.url;
  console.log("Smtp2go MCP URL:", composioMCPUrl);

What's happening:

create spins up a short-lived MCP HTTP endpoint for this user
The toolkits array contains "smtp2go" for Smtp2go access
session.mcp.url is the MCP URL that Mastra's MCPClient will connect to

Configure Mastra MCP client and fetch tools

typescript

const mcpClient = new MCPClient({
    id: composioUserID as string,
    servers: {
      nasdaq: {
        url: new URL(composioMCPUrl),
        requestInit: {
          headers: session.mcp.headers,
        },
      },
    },
    timeout: 30_000,
  });

console.log("Fetching MCP tools from Composio...");
const composioTools = await mcpClient.getTools();
console.log("Number of tools:", Object.keys(composioTools).length);

What's happening:

MCPClient takes an id for this client and a list of MCP servers
The headers property includes the x-api-key for authentication
getTools fetches the tool definitions exposed by the Smtp2go toolkit

Create the Mastra agent

typescript

const agent = new Agent({
    name: "smtp2go-mastra-agent",
    instructions: "You are an AI agent with Smtp2go tools via Composio.",
    model: "openai/gpt-5",
  });

What's happening:

Agent is the core Mastra agent
name is just an identifier for logging and debugging
instructions guide the agent to use tools instead of only answering in natural language
model uses openai("gpt-5") to configure the underlying LLM

Set up interactive chat interface

typescript

let messages: AiMessageType[] = [];

console.log("Chat started! Type 'exit' or 'quit' to end.\n");

const rl = readline.createInterface({
  input: process.stdin,
  output: process.stdout,
  prompt: "> ",
});

rl.prompt();

rl.on("line", async (userInput: string) => {
  const trimmedInput = userInput.trim();

  if (["exit", "quit", "bye"].includes(trimmedInput.toLowerCase())) {
    console.log("\nGoodbye!");
    rl.close();
    process.exit(0);
  }

  if (!trimmedInput) {
    rl.prompt();
    return;
  }

  messages.push({
    id: crypto.randomUUID(),
    role: "user",
    content: trimmedInput,
  });

  console.log("\nAgent is thinking...\n");

  try {
    const response = await agent.generate(messages, {
      toolsets: {
        smtp2go: composioTools,
      },
      maxSteps: 8,
    });

    const { text } = response;

    if (text && text.trim().length > 0) {
      console.log(`Agent: ${text}\n`);
        messages.push({
          id: crypto.randomUUID(),
          role: "assistant",
          content: text,
        });
      }
    } catch (error) {
      console.error("\nError:", error);
    }

    rl.prompt();
  });

  rl.on("close", async () => {
    console.log("\nSession ended.");
    await mcpClient.disconnect();
    process.exit(0);
  });
}

main().catch((err) => {
  console.error("Fatal error:", err);
  process.exit(1);
});

What's happening:

messages keeps the full conversation history in Mastra's expected format
agent.generate runs the agent with conversation history and Smtp2go toolsets
maxSteps limits how many tool calls the agent can take in a single run
onStepFinish is a hook that prints intermediate steps for debugging

Complete Code

Here's the complete code to get you started with Smtp2go and Mastra AI:

typescript

import "dotenv/config";
import { openai } from "@ai-sdk/openai";
import { Agent } from "@mastra/core/agent";
import { MCPClient } from "@mastra/mcp";
import { Composio } from "@composio/core";
import * as readline from "readline";

import type { AiMessageType } from "@mastra/core/agent";

const openaiAPIKey = process.env.OPENAI_API_KEY;
const composioAPIKey = process.env.COMPOSIO_API_KEY;
const composioUserID = process.env.COMPOSIO_USER_ID;

if (!openaiAPIKey) throw new Error("OPENAI_API_KEY is not set");
if (!composioAPIKey) throw new Error("COMPOSIO_API_KEY is not set");
if (!composioUserID) throw new Error("COMPOSIO_USER_ID is not set");

const composio = new Composio({ apiKey: composioAPIKey as string });

async function main() {
  const session = await composio.create(composioUserID as string, {
    toolkits: ["smtp2go"],
  });

  const composioMCPUrl = session.mcp.url;

  const mcpClient = new MCPClient({
    id: composioUserID as string,
    servers: {
      smtp2go: {
        url: new URL(composioMCPUrl),
        requestInit: {
          headers: session.mcp.headers,
        },
      },
    },
    timeout: 30_000,
  });

  const composioTools = await mcpClient.getTools();

  const agent = new Agent({
    name: "smtp2go-mastra-agent",
    instructions: "You are an AI agent with Smtp2go tools via Composio.",
    model: "openai/gpt-5",
  });

  let messages: AiMessageType[] = [];

  const rl = readline.createInterface({
    input: process.stdin,
    output: process.stdout,
    prompt: "> ",
  });

  rl.prompt();

  rl.on("line", async (input: string) => {
    const trimmed = input.trim();
    if (["exit", "quit"].includes(trimmed.toLowerCase())) {
      rl.close();
      return;
    }

    messages.push({ id: crypto.randomUUID(), role: "user", content: trimmed });

    const { text } = await agent.generate(messages, {
      toolsets: { smtp2go: composioTools },
      maxSteps: 8,
    });

    if (text) {
      console.log(`Agent: ${text}\n`);
      messages.push({ id: crypto.randomUUID(), role: "assistant", content: text });
    }

    rl.prompt();
  });

  rl.on("close", async () => {
    await mcpClient.disconnect();
    process.exit(0);
  });
}

main();

Conclusion

You've built a Mastra AI agent that can interact with Smtp2go through Composio's Tool Router. You can extend this further by:

Adding other toolkits like Gmail, Slack, or GitHub
Building a web-based chat interface around this agent
Using multiple MCP endpoints to enable cross-app workflows

TOOLS

Supported Tools

Every Smtp2go action and event your agent gets out of the box.

Search Email Activity

Tool to search activity events like sends, opens, clicks, and bounces.

Add Allowed Sender

Tool to add a new allowed sender email address.

Remove Allowed Sender

Tool to remove a sender email address from the allowed senders list.

Update Allowed Senders

Tool to update (replace) the entire allowed senders list in your SMTP2GO account.

View Allowed Senders

Tool to view the list of allowed senders configured in your account.

Add Sender Domain

Tool to add a new sender domain for SPF/DKIM verification.

Search SMTP2GO Emails

Tool to search sent emails.

Add IP Allow List

Tool to add a public IP address to your account's IP allow list.

Remove IP from Allow List

Tool to remove an IP address from your account's IP allow list.

View IP Allow List

Tool to view the list of IP addresses in your IP allow list.

View Received SMS

Tool to retrieve received SMS replies for your SMTP2GO account.

Get Email Bounces Stats

Tool to retrieve email bounces statistics.

Email Cycle Statistics

Tool to retrieve current email cycle/quota statistics.

Email History Statistics

Tool to retrieve email history statistics.

Email Spam Statistics

Tool to retrieve email spam report statistics.

Email Unsubscription Stats

Tool to retrieve email unsubscribe statistics.

Search Subaccounts

Tool to search subaccounts.

Subaccounts Usage

Tool to retrieve usage statistics for subaccounts.

Add to Suppression List

Tool to add email addresses or domains to the suppression list.

Remove suppression entry

Tool to remove an email address or domain from the suppression list.

View Suppression List

Tool to view the suppression list.

Edit Email Template

Tool to edit details of an existing email template.

Search Email Templates

Tool to search your collection of email templates by ID or name.

View Email Template

Tool to view details of a specific email template.

Add SMTP User

Tool to add a new SMTP user.

Edit SMTP User

Tool to edit details of an existing SMTP user.

Remove SMTP User

Tool to remove an SMTP user from your account.

View SMTP Users

Tool to list all SMTP users configured on your account.

Add Webhook

Tool to create a new webhook.

Edit Webhook

Tool to edit an existing webhook’s settings.

Remove webhook

Tool to remove a webhook.

View Webhooks

Tool to view all webhooks configured in your account.

FRAMEWORKS

How to build Smtp2go MCP Agent with another framework

OpenAI Agents SDK

Use Smtp2go MCP with OpenAI Agents SDK

Claude Agent SDK

Use Smtp2go MCP with Claude Agent SDK

Claude Code

Use Smtp2go MCP with Claude Code

Claude Cowork

Use Smtp2go MCP with Claude Cowork

Codex

Use Smtp2go MCP with Codex

OpenClaw

Use Smtp2go MCP with OpenClaw

Hermes

Use Smtp2go MCP with Hermes

CLI

Use Smtp2go MCP with CLI

Google ADK

Use Smtp2go MCP with Google ADK

LangChain

Use Smtp2go MCP with LangChain

Vercel AI SDK

Use Smtp2go MCP with Vercel AI SDK

LlamaIndex

Use Smtp2go MCP with LlamaIndex

CrewAI

Use Smtp2go MCP with CrewAI

MORE TOOLKITS

Explore Other Toolkits

Toolkit marketplace

Apilio

Api KeyBasic

Apilio is a home automation platform that lets you connect and control smart devices from different brands. It helps you build flexible automations with complex conditions, schedules, and integrations.

Basin

Api Key

Basin is a no-code form backend for quickly setting up reliable contact forms. It lets you collect and manage form submissions without writing any server-side code.

Bouncer

Api Key

Bouncer is an email validation platform that verifies the authenticity of email addresses in real-time and batch. It helps boost deliverability and reduce bounce rates for your communications.

Conveyor

Api Key

Conveyor is a platform that automates security reviews with a Trust Center and AI-driven questionnaire automation. It streamlines compliance and vendor security processes for faster, hassle-free reviews.

FAQ

Frequently asked questions

With a standalone Smtp2go MCP server, the agents and LLMs can only access a fixed set of Smtp2go tools tied to that server. However, with the Composio Tool Router, agents can dynamically load tools from Smtp2go and many other apps based on the task at hand, all through a single MCP endpoint.

Yes, you can. Mastra AI 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 Smtp2go tools.

Yes, absolutely. You can configure which Smtp2go 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 Smtp2go data and credentials are handled as safely as possible.

Start with Smtp2go.It takes 30 seconds.

Managed auth, hosted MCP servers, and every Smtp2go tool your agent needs.Free to start.

Start building

Customer stories

Teams ship real agents on Composio

GET STARTED FOR FREE BOOK A DEMO

Karan skipped his own birthday party to fix our critical issue. It was 10pm and he diverted his Waymo to help us instead. This really sets the bar — it shows the commitment you need when users rely on your software.

Harsha Gaddipati

Co-founder, Slashy

A lot of students tell us that the moment their connected tools start talking to each other inside Opennote feels almost magical. The agent just knows them, and it's immensely helped keep new users on the platform.

Abhi Arya

Co-founder, Opennote

We chose Composio over Pipedream because it delivered depth where it mattered — niche tools and tricky edge cases other platforms simply ignored. That gave us confidence to scale without compromising.

Nirman Dave

CEO, Zams

As a solo builder, shipping fast is life or death. The only way I can outcompete incumbents is by outmanoeuvring them. Getting bogged down managing agent auth would have been a death sentence.

Ryan Yu

Founder, Extra Thursday

Before Composio, adding tool integrations was slow and resource-intensive. Each one could take weeks of engineering time, and maintaining them meant constantly keeping up with API changes.

Tomisin Jenrola

Founder & CEO, SwarmZero

With hands-on help from their founder, we integrated Gmail and Google Drive in just 30 minutes. This level of personal support and commitment is exactly what startups should strive for.

Jerome Leclanche

Co-Founder, Ingram Technologies

How to integrate Smtp2go MCP with Mastra AI

Connect Smtp2go without auth hassles

Introduction

Also integrate Smtp2go with

TL;DR

What is Mastra AI?

What is the Smtp2go MCP server, and what's possible with it?

What is the Composio tool router, and how does it fit here?

What is Composio SDK?

How the Composio SDK works

Step-by-step Guide

Prerequisites

Getting API Keys for OpenAI and Composio

Install dependencies

Set up environment variables

Import libraries and validate environment

Create a Tool Router session for Smtp2go

Configure Mastra MCP client and fetch tools

Create the Mastra agent

Set up interactive chat interface

Complete Code

Conclusion

Supported Tools

How to build Smtp2go MCP Agent with another framework

OpenAI Agents SDK

Claude Agent SDK

Claude Code

Claude Cowork

Codex

OpenClaw

Hermes

CLI

Google ADK

LangChain

Vercel AI SDK

LlamaIndex

CrewAI

Explore Other Toolkits

Apilio

Basin

Bouncer

Conveyor

Frequently asked questions

What are the differences in Tool Router MCP and Smtp2go MCP?+

Can I use Tool Router MCP with Mastra AI?+

Can I manage the permissions and scopes for Smtp2go while using Tool Router?+

How safe is my data with Composio Tool Router?+

Start with Smtp2go.It takes 30 seconds.

Teams ship real agents on Composio