The Mailbox Sizes report shows you the current size of each user's mailbox in your Office 365 Environment. The chart displays the 20 largest mailboxes as a bar graph, and you can display the Warning or Prohibit Send quotas by selecting their series items in the legend.
The Data Table
The data table lists each user, the size of their mailbox, and the various quotas they have. You can add, remove or re-order these columns to display additional information such as Deleted Items.
This report can be filtered, allowing you to generate bespoke reports about the mailbox sizes in a particular Department, Country or any other category you choose.
As with all of the reports, this information can be customized, filtered and scheduled.