Empty Spam
Any website enquiries that are identified as not genuine will be sent to your Spam folder - and unlike a genuine Enquiry, you will not receive an email notification for them.
You can access your Spam folder by logging into your admin account and clicking the tab at the top of your Enquiries page.
Login as admin > Enquiries > Spam
Whilst you can use the Delete button to individually delete Enquiries, you're also able to use the Empty Spam button to delete all Spam Enquiries.