Rest assured, crossing the monthly email limit does not block you from sending emails. Emails requests, above the monthly allocated credits of the monthly plan, are calculated at the end of your billing cycle and are included in the invoice for the upcoming month. It reflects as an 'Overage' in your invoice.
For more information about our Overage policy, you can refer to the below link:
https://emaildocs.netcorecloud.com/docs/what-is-overage-and-how-it-is-calculated