The Mailbox Over Quota report shows you all mailboxes that are currently over their send or receive quota in your Office 365 Environment. You can change which data is displayed on the chart by selecting or deselecting the different 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 Department.
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.