The dovecot 2.4 release branch has made breaking changes which result in it being incompatible with any <= 2.3 configuration file.

Thus, the dovecot service will no longer be able to start until the configuration file was migrated, requiring manual intervention.

For guidance on the 2.3-to-2.4 migration, please refer to the following upstream documentation: Upgrading Dovecot CE from 2.3 to 2.4

Furthermore, the dovecot 2.4 branch no longer supports their replication feature, it was removed.

For users relying on the replication feature or who are unable to perform the 2.4 migration right now, we provide alternative packages available in [extra]:

• dovecot23
• pigeonhole23
• dovecot23-fts-elastic
• dovecot23-fts-xapian

The dovecot 2.3 release branch is going to receive critical security fixes from upstream until stated otherwise.