WildDuck Mail Server

WildDuck is a scalable no-SPOF IMAP/POP3 mail server. WildDuck uses a distributed database (sharded + replicated MongoDB) as a backend for storing all data, including emails.
WildDuck is part of the Zone Mail Suite — together with Haraka (inbound SMTP) and ZoneMTA (outbound SMTP), it forms a complete email server solution. See the Architecture Overview for how the components work together.
WildDuck tries to follow Gmail in product design. If there's a decision to be made then usually the answer is to do whatever Gmail has done.
Requirements
- MongoDB to store all data
- Redis for pubsub, caching, and rate limiting
- Node.js version 16 or later
Optional requirements
- Redis Sentinel for automatic Redis failover
- ElasticSearch for full-text search
- Build tools to install optional dependencies that need compiling
WildDuck can be installed on any Node.js compatible platform.
No-SPOF architecture
Every component of the WildDuck mail server can be replicated which eliminates potential single point of failures.

Storage
Attachment de-duplication and compression gives up to 56% of storage size reduction.

License
WildDuck Mail Agent is licensed under the European Union Public License 1.2 or later.