This is a working configuration for qmail/vpopmail/dovecot servers. The connection is done by means of the sql driver.
Rename local.conf.template to local.conf. Eventually add there your customizations.
You can find more info and ask for support at https://notes.sagredo.eu/en/qmail-notes-185/installing-dovecot-and-sieve-on-a-vpopmail-qmail-server-28.html.