Email notification

Hi I have an online form which, when submitted, sends an email notification to specified people when certain fields are populated. When those fields are not populated, it still enters the details on the calendar view, which is fine, that's how I want it to be. However, now, all of a sudden, ALL submitted forms are being emailed, regardless of whether or not those fields are populated. I have changed nothing in the settings so why is this suddenly happening? It's so annoying when you change things without saying anything to anyone!!! Kim