Your Exchange quota includes all your email, attachments, calendaring data, task items, and more. We strongly recommend that you manage your quota by deleting items you do not need and clear out the deleted items weekly. Your ACCC Exchange mailbox grows as you create and receive items. When you delete items, the size of the Outlook Data File (.pst and .ost) file might not decrease in proportion to the data that you deleted. There are several ways to manage your mailbox and reduce the size of the data file.