list mailbox sizes in exchange 2010 very easy with this simple powershell script.
Get-MailboxStatistics –Server %MAILBOXSERVERNAME% | Sort-Object -Property TotalItemSize -Descending | FT DisplayName,TotalItemSize,ItemCount > C:/temp/output.csv (txt)
this creates a csv or a txt file with 3 columns
it looks like this:
| Display name | Item Size | total items |
| Team4 | 10.49 KB (10,738 bytes) | 4 |
| Team2 | 10.49 KB (10,738 bytes) | 4 |
| Team1 | 10.49 KB (10,738 bytes) | 4 |
| Team5 | 10.49 KB (10,738 bytes) | 4 |
| Team3 | 10.49 KB (10,738 bytes) | 4 |
is you substract > C:/temp/output.csv (txt) the result will be displayed in the powershell command prompt.