Here is a nice way to see who is using up the most space on your mailbox servers.
Get
-Mailbox
-ResultSize
Unlimited | Get
-MailboxStatistics
|
Select
DisplayName,
TotalItemSize,ItemCount,
Database,LastLogonTime,LastLoggedOnUserAccount | Sort
TotalItemSize
-Descending
|
ConvertTo-Html
-Title
"Mailbox Stats"
|
Out-file
"C:\MailboxStatistics.html