View Mailbox Size in Exchange Server 2003/2007/2010

For Exchange 2003:
Open Exchange System Manager from the Programs folder in Start Menu and head to Administrative Groups.

Select the first administrative group -> Servers -> Your server name -> First Storage group -> Mailbox Store -> Mailboxes
Here, you will see all the mailbox size and item counts.

For Exchange 2007:

Exchange Management Console does not allow us to see the mailbox count and item count.
For this to see open Exchange Management Shell and run this command:

Get-MailboxStatistics -database “Mailbox Database” | Select DisplayName, LastLoggedOnUserAccount, ItemCount, TotalItemSize, LastLogonTime, LastLogoffTime | Format-Table
You will see all the mailbox size in Bytes and the item count for each mailbox. Here is the screenshot:



This is the command to export this details to a CSV file:
Get-MailboxStatistics -Database “Mailbox Database” | Select DisplayName, LastLoggedOnUserAccount, ItemCount, TotalItemSize, LastLogonTime, LastLogoffTime | Export-CSV test.csv

For Exchange 2010:

You can use the Exchange Management Console to view who last logged on to a mailbox, the last logon date and time, the mailbox size, and the message count by completing these steps:
1. Expand the Recipient Configuration node and then select the Mailbox node.
2. Double-click the mailbox with which you want to work.
3. On the General tab, the Last Logged On By text box shows who last logged on to the mailbox, and the Modified entry shows the date and time the mailbox was last modified.
4. On the General tab, the Total Items and Size (KB) areas show the number of messages in the mailbox and the current mailbox size in kilobytes, respectively.

If you want to view similar information for all mailboxes on a server, the easiest way is to use the Get-MailboxStatistics cmdlet. Here are some examples of using this cmdlet.
Syntax :
Get-MailboxStatistics -Identity 'Identity' [-Archive ] [-DomainContoller DomainController] [-IncludeMoveHistory ] [-IncludeMoveReport ] Get-MailboxStatistics -Server 'Server' | -Database 'Database' [-DomainContoller DomainController]

Usage :
Get-MailboxStatistics -Server 'corpsvr127'
Get-MailboxStatistics -Database 'Engineering Primary'
Get-MailboxStatistics –Identity 'cpandl\williams'