This tutorial teaches you how to view the storage capacity of your Office 365 account in Outlook 2013.
Your quota on the Office 365 system is taken up by email, calendaring and any other information that you store in Office 365. Queen’s offers 25 GB of space for every user on Office 365. Additional storage space is available for a fee.
It is important to be aware of your quota status because you will be unable to send mail if you exceed your limit. To clean up your data and free up space, remember to periodically delete the items you no longer need, and empty the Deleted Items folder.