WildDuck
A modern IMAP/POP3 mail server built on Node.js and MongoDB, designed for horizontal scale
WildDuck is an open-source IMAP/POP3 mail server written in Node.js that stores all data in MongoDB. It is designed to be combined with Haraka for inbound SMTP and ZoneMTA for outbound SMTP to form a complete mail server, and it targets deployments of 1000 or more accounts that need horizontal scaling.
It provides IMAP4rev1 with IDLE, CONDSTORE, COMPRESS, SPECIAL-USE, UTF8, and QUOTA, plus Unicode support for internationalized addresses, folder names, and headers. Accounts, mailboxes, messages, filters, auto-replies, and DKIM are managed through a REST API. Security features include 2FA (TOTP and WebAuthn), application passwords, PGP encryption, and audit logs. MongoDB sharding and stateless instances allow scaling behind a load balancer, with MongoDB replica sets, Redis Sentinel, and multiple app servers for redundancy.
WildDuck is licensed under EUPL 1.2 and is available as source code, with installation via scripted install, Docker, or manual setup. A live demo offers a free @wildduck.email address for testing with the web client or an IMAP app; outbound delivery from that domain is disabled.
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