Mailbox doesn't exist: test

I’ve been getting an error when trying to save mail based on address extensions where dovecot is not creating the mailbox:

dovecot: lda(user@example.com): msgid=Balhs-user@example.net: save failed to open mailbox test: Mailbox doesn't exist: test

Is this is as simple as adding lda_mailbox_autocreate = yes to my conf file, and does it go at the ‘top’ level of the file, or does it need to be in some sort of clause?

-- There is something to be said for grace and respect but humour alway helps - Toby Morris