Wildduck Mail Server
Scalable Design
Supports 1000+ accounts with horizontal scaling.
WildDuck is a modern IMAP/POP3 server built on Node.js and MongoDB. Bundle it with Haraka (inbound SMTP) and ZoneMTA (outbound SMTP) for a complete mail server. Best suited for 1000+ accounts that need horizontal scaling. For smaller setups, consider Postfix+Dovecot. Scalable Everything is stored in MongoDB with sharding support. All instances are stateless — add more behind a load balancer to increase throughput.
