When Does the Mail for Workato 500 Email Limit Reset in AU Data Centre?

Quick question. I'm using Mail for Workato as an error/warning alert method and due to some unusual circumstances, have blown past the 500 per day limit. We are in the AU data centre. Does anyone know what time of day the email limit counter is reset? Or is it a sliding window of the past 24 hours? Does it include all three environments (DEV, TEST, and PROD) or does each one get 500? I'm going to move the alerts to use a company Outlook account instead, but I'm still curious to know the answers.