docker compose -f /opt/mailcow-dockerized/docker-compose.yml exec mysql-mailcow mysql -u mailcow -p mailcow -e 'SELECT COUNT(*) AS q FROM quarantine;'

This runs a direct SQL query against the mailcow database, here counting rows in the quarantine table. Useful to confirm the quarantine really is empty after a purge. The password in -p matches the one stored in mailcow.conf.