Exchange Mail Size from Exchange PowerShell
Get-MailboxStatistics | Sort-Object TotalItemSize -Descending | ft DisplayName,@{label=”TotalItemSize(KB)”;expression={$_.TotalItemSize.Value.ToKB()}},ItemCount
Get-MailboxStatistics -Database “Mailbox Database” | Select DisplayName, ItemCount, TotalItemSize | Export-CSV c:\test.csv