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WildDuck Mail Server

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 account and message data
  • Redis for pubsub, caching, and rate limiting
  • Node.js version 22.19.0 or later

Optional requirements

  • Redis Sentinel for automatic Redis failover
  • OpenSearch for experimental message indexing
  • S3-compatible object storage for attachment payloads
  • 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.