wildduck is a free, open-source IMAP and POP3 email server built for horizontal scaling. See features, architecture, licensing, and self-hosting details.
wildduck is an open-source IMAP and POP3 email server built on Node.js and MongoDB, created by developer Andris Reinman and released as part of the Zone Mail Suite under the EUPL 1.2 license.
Unlike traditional mail servers that store mailboxes on the filesystem, wildduck stores every account, mailbox, and message in MongoDB, which allows it to scale horizontally across sharded database clusters.
It is explicitly designed for larger deployments, targeting organizations managing 1,000 or more mailboxes that need to scale beyond a single server, and is commonly paired with Haraka and ZoneMTA to form a complete inbound and outbound mail server stack.
wildduck provides a first-class IMAP4rev1 implementation with IDLE, CONDSTORE, COMPRESS, SPECIAL-USE, UTF8, and QUOTA support, along with full support for internationalized addresses, folder names, and headers.
Because every instance is stateless, administrators can run multiple wildduck instances behind a load balancer to increase throughput as mailbox volume grows, rather than scaling a single monolithic server.
The entire server is managed through a REST API covering accounts, mailboxes, messages, filters, auto-replies, and DKIM keys, and it supports application-specific passwords and multi-factor authentication without requiring root privileges.
wildduck is free, open-source software licensed under the EUPL 1.2, with no official paid tier or license fee.
Since it is self-hosted, organizations only bear their own infrastructure costs, including servers and MongoDB hosting, rather than paying a subscription to a vendor.
There is no managed wildduck-as-a-service offering from the core project; deployment and scaling are handled by the organization running it.
wildduck is an open-source IMAP and POP3 email server built on Node.js and MongoDB, designed for scalable, API-driven mail hosting.
Yes, wildduck is free and open source under the EUPL 1.2 license, with no official paid tier.
No, wildduck focuses on IMAP and POP3 mailbox access; it is typically paired with Haraka for inbound and ZoneMTA for outbound SMTP.
It stores accounts, mailboxes, and messages in MongoDB rather than on the filesystem, which supports sharding and horizontal scaling.
wildduck was created by developer Andris Reinman, based in Tallinn, Estonia, as part of the Zone Mail Suite.
It is explicitly designed for larger deployments of 1,000 or more mailboxes; smaller setups may be better served by simpler mail servers.
Yes, all management, including accounts, mailboxes, filters, and DKIM keys, is handled through a REST API.
Yes, it supports application-specific passwords and multi-factor authentication.