io.github.friendlygeorge/resend-mcp-server

Resend MCP Server

An MCP server for Resend — connect any MCP-compatible client to the Resend transactional email API.

What is this?

An MCP (Model Context Protocol) server that gives AI assistants and agents full access to Resend's email API — send single or batch emails, manage sending domains, API keys, audiences, and contacts — through natural language.

Use it with Claude Desktop, Cursor, Windsurf, Cline, Continue, or any MCP-compatible client to send emails, manage infrastructure, and build automation around email.

Why use this?

• 18 built-in tools — covers sending (single + batch), domains, API keys, audiences, and contacts
• Send emails by talking — "send a welcome email to jane@example.com" just works
• Manage your infrastructure — create/verify/delete domains, mint/revoke API keys, manage contacts
• Batch sending — send up to 100 emails in a single API call
• Full contact CRUD — create, read, update, and delete contacts across audiences
• Rate-limited automatically — respects Resend's 10 req/s free tier, retries on 429
• Works with every MCP client — Claude Desktop, Cursor, Windsurf, Cline, Continue, and more

Quick Start

Add to your MCP client config (e.g. claude_desktop_config.json):

{
  "mcpServers": {
    "resend": {
      "command": "npx",
      "args": ["-y", "resend-mcp-server"],
      "env": {
        "RESEND_API_KEY": "re_xxxxxxxxxxxx"
      }
    }
  }
}

Get a free API key at resend.com/api-keys.

Use it

Ask your AI assistant things like:

• "Send an email to jane@example.com thanking her for signing up"
• "List the last 5 emails I sent"
• "What happened to email ID abc-123?"
• "Create a new sending domain for mail.acme.com"
• "Verify domain domain-xyz"
• "Mint a new API key called 'production-server'"
• "Add jane@example.com to audience audience-1"

Tools

Use Cases

Transactional Email Automation

"Send a welcome email to every new signup" — automate onboarding flows, receipts, and notifications through natural language. No more switching between email dashboards.

Domain Management

"Add mail.acme.com as a sending domain and verify it" — manage DNS records, DKIM, and SPF through your AI assistant instead of logging into Resend's dashboard.

Contact & Audience Management

"Add jane@example.com to my VIP audience" — build and segment contact lists without touching a spreadsheet. Full CRUD on contacts and audiences.

Batch Campaigns

"Send this newsletter to all contacts in audience-1" — batch-send up to 100 emails in one call. Perfect for newsletters, product announcements, or re-engagement campaigns.

Infrastructure Audit

"List all my API keys and domains" — audit your Resend setup in seconds. See which keys are active, which domains are verified, and clean up stale resources.

Security

• API key required — Resend API key is passed via environment variable, never logged or stored in files.
• No local file access — does not read or write any files on your machine.
• No shell access — does not execute commands or spawn processes.
• Rate-limited — automatically caps requests at ~9 req/s to stay within Resend's free tier.
• Open source — MIT licensed. Inspect the code at GitHub.

Troubleshooting

Rate limit errors (429)

The server auto-retries on 429 with a 2s backoff. Free tier allows 10 req/s. The server caps at ~9 req/s to stay safe. If you hit this frequently, consider upgrading your Resend plan.

"Invalid API key" errors

Verify your RESEND_API_KEY starts with re_ and is active at resend.com/api-keys. Keys take up to 30 seconds to propagate after creation.

Server won't start

Make sure Node.js 18+ is installed: node --version. If using npx, ensure npm is up to date: npm install -g npm@latest.

MCP client can't connect

Verify the config path is correct. Claude Desktop uses ~/Library/Application Support/Claude/claude_desktop_config.json on macOS and %APPDATA%\Claude\claude_desktop_config.json on Windows. Restart the client after config changes.

Emails not delivering

Check list_emails for delivery status. Common issues: missing DNS records (run verify_domain), bounce due to invalid address, or domain not yet verified. Resend's dashboard shows detailed webhook events.

Requirements

• Node.js 18+
• A Resend account and API key (RESEND_API_KEY)

Rate Limits

The server automatically rate-limits requests to ~9 calls/second to stay safely under Resend's free-tier limit of 10 req/s. If you hit a 429 anyway, it waits 2s and retries once.

Development

git clone https://github.com/friendlygeorge/resend-mcp-server.git
cd resend-mcp-server
npm install
npm run build
RESEND_API_KEY=re_xxxx npm start

License

MIT