ImapFlow is a modern, promise-based IMAP client library for Node.js that simplifies email protocol interactions by automatically handling IMAP extensions and providing a clean API. It's designed for developers building email applications who want reliable IMAP access without needing deep protocol expertise, with built-in features like mailbox locking, message streaming, and TypeScript support. The library works seamlessly with various email providers including Gmail, Outlook, and Yahoo, and was created as the foundation for EmailEngine, a self-hosted email gateway.