Resend
Developer-first email API with an official MCP server — agents can send transactional emails, manage contacts, and track delivery.
About
Resend is a modern transactional email API that has embraced agent use through an official MCP server. While not built exclusively for agents like AgentMail, Resend's clean API design and MCP support make it a practical choice for agents that need to send emails — transactional notifications, reports, alerts, or user communications. The React-based email templating system (via the open-source react-email library) makes it easy to build professional emails programmatically.
The MCP server (available at resend.com/mcp) supports both stdio and HTTP transport modes, exposing tools for sending emails, managing contacts and audiences, handling domain configuration, and tracking delivery events via webhooks. Agents authenticate with a simple API key, and SDKs are available in over 10 languages — the broadest coverage of any email API.
Resend reached 1 million users in December 2025. The free tier includes 3,000 emails per month (100/day limit) on a single domain. Paid plans start at $20/month for 50,000 emails with unlimited domains. DKIM, SPF, and DMARC are handled automatically.