Dovecot 2.4 removed one of the mail server's most outstanding features: being able to replicate between two servers, even in an active-active scenario if desired. The actual sync code stays in place, but the replication orchestrator was removed.

On the other hand, the same release introduces improvements to two APIs: the event API now allows reacting to pretty much anything happening in Dovecot using an HTTP server, while the doveadm HTTP allows to trigger synchronization with another server.

We'll have a look on Dovecot 2.3's implementation of replication, checking out alternative solutions to replication to finally look into a Golang-based solution that does not require forking the mail server codebase.