By default, for any cloud service, Microsoft sets an aggregate monthly usage quota that is calculated across all of a customer's subscriptions. We understand that at times your needs might exceed these limits. You can contact customer service at any time, so we can understand your needs and adjust these limits appropriately. For Service Bus, the aggregate usage quotas are as follows:
5 billion messages
2 million relay hours
Although we reserve the right to disable an account that exceeds its monthly usage quotas, we provide e-mail notification, and we make multiple attempts to contact the customer before taking any action. Customers that exceed these quotas are still responsible for excess charges.