docker compose -f /opt/mailcow-dockerized/docker-compose.yml exec mysql-mailcow mysqldump -u mailcow -p mailcow mailcow | gzip > /backup/mailcow-db.sql.gz

mysqldump exports the whole mailcow schema and data, piped through gzip into a dated backup file. The dump contains mailboxes, aliases, domains, and quarantine state but not maildirs. Restore it with mysql < backup.sql if the database is ever lost.