I recently discovered the Wild Duck mailserver, which sounds great from their description:
WildDuck is a modern mail server software for IMAP and POP3. Modern being scalable, unicode-first and API-controlled.
Written from scratch, including web mail client (supporting OpenPGP via Mailvelope), using Node.js.
However it’s unclear to me what exactly it is – a replacement for Dovecot, or Postfix, or both?
WildDuck can be used as a replacement for Dovecot but it (and its integrations with ZoneMTA and Haraka) is mostly meant to replace the entire stack. WildDuck has been mainly built with focus on scalability and high availability, so you could set up a cluster of servers and host a large number of users / emails on that cluster with the option of loosing some servers while keep the service still available. If you are going to run your email stack in just one server and do not care about horizontal scaling too much then there might be better (more proven) options out there.
@andris9 Welcome and thanks for your reply.
So Wildduck doesn’t include a new MTA of it’s own, but relies on integrations with others like you mentioned, and doesn’t support Postfix?
WildDuck would work with Postfix using LMTP but in that setup it would loose all its advantages. WildDuck has deep integration with Haraka as MX and ZoneMta as outbound MTA. The main difference is in queue handling - in this setup queue files are never stored to disk but in a MongoDB database. This in turn gives the option of removing any server in production with no data loss and not affecting the service (assuming all servers are duplicated etc). If you remove a Postfix server you loose all emails that are in the queue of that instance. All ZoneMta server share the same queue, so it does not matter if there are more or less servers at any given time.