·        http://support.microsoft.com/kb/328841

·        http://support.microsoft.com/kb/245822

·        Exchange 2003 - http://support.microsoft.com/kb/823166

·        Exchange 2007 - http://technet.microsoft.com/en-us/library/bb332342(EXCHG.80).aspx

·        Exchange 2010 - http://technet.microsoft.com/en-us/library/bb332342.aspx

Use Exchange Server 2010 SP1 Help content to help you plan, deploy and manage your Exchange 2010 SP1 organization

http://www.microsoft.com/downloads/en/details.aspx?FamilyID=2685440c-8e55-463a-ab96-102eddf8a7c4

An easy way to find database whitespacee in Exchange 2010 (since there are no 1221 events),is by using PowerShell

In the Exchange Management Shell, use the following cmdlet :

Get-MailboxDatabase -Status | fl  Server,Name,AvailableNewMailboxSpace