Find Largest Mailboxes on Exchange 2010 (PowerShell)

Finding largest mailboxes for future growth prediction and disk space planning.

Open Exchange Management Shell as Administrator and run the following commands:

[PS]> Get-MailboxDatabase

Name                          Server       Recovery   ReplicationType
----                          ------       --------   ---------------
Mailbox Database 0711036955   INTERNALDC   False      None

[PS]> Get-MailboxDatabase "Mailbox Database 0711036955" | Get-MailboxStatistics | Sort TotalItemSize -desc | ft DisplayName,TotalItemSize

DisplayName              TotalItemSize
-----------              -------------
Partick                  10.47 GB (11,241,141,931 bytes)
Sandy                    7.101 GB (7,624,803,713 bytes)
Gary                     2.05 GB (2,201,104,109 bytes)
Administrator            14.12 KB (14,457 bytes)

Another ways of doing that would be:

[PS]> Get-Mailbox | Get-MailboxStatistics | Sort-Object TotalItemSize -des | ft DisplayName,TotalItemSize

[PS]> Get-MailboxStatistics -server SERVERNAME | sort-object -Property TotalItemSize -des | select-object DisplayName,ItemCount,TotalItemSize -first 10