Fixing the dovecot_config_version Error in Dovecot 2.4

Dovecot 2.4 refuses to start without dovecot_config_version — here's how to fix it.

After upgrading to Dovecot 2.4, the server refuses to start with "dovecot_config_version not set." This is by design — Dovecot 2.4 requires a complete configuration rewrite. Here's what you need to know.

Dovecot 2.4 introduced a mandatory dovecot_config_version setting. Without it, the server won't start. This isn't a bug — it's Dovecot's way of forcing you to review your entire configuration, because the syntax has changed significantly.

Add this to the top of your dovecot.conf:

dovecot_config_version = 2.4.0

But don't stop there. Simply adding the version line will get Dovecot to start, but your old 2.3 configuration likely contains deprecated settings that will cause problems. The mail_location setting, SSL certificates, and SQL authentication have all changed syntax.

Willem's complete migration guide covers every breaking change — from variable notation to encryption settings to the Sieve plugin.