To increase the value of email that applications send to users and to give users control over what email they want to receive, we are rolling out a user feedback-based allocation system for email early next week. The static limit on the number of email messages an application can send to a given user per day will be determined primarily by the rate at which users disable email from within an email message. Based upon positive data, the opt-out link will be moved to the bottom of the email for a significant percentage of applications. Since having the link at the top generally increases the rate that users click on it, clicks from the bottom of an email will be weighted differently than clicks at the top, so that scores will be based on the quality of the communication, not the location of the message. We will also take into account fluctuations in the amount of email sent, so your email limit will not decrease if you start sending less email overall.
You can view your allocations and metrics on the Insights stats page. You can retrieve your allocations through the API with Admin.getAllocation.