Could you create a date formula field that changes to the first day of the month each month on a form and set up your email notification to only go out when that date field changes to the first day of the month? I know you need to have a "trigger" or modification to the record to trigger a notification but I wonder if the changing of that date field would trigger the notification. Or, is there a date formula where you could have the date change every 30 days based on the record's date created that might work? I'd love to use the subscription instead, but the notification will be going to non-users. The goal is to send clients a list of their project information every month. Thanks!