This is best for when you need to kill off all traces of a message on your Exchange 2007/2010 server. Examples include e-mail virus, obnoxious chain letters or even angry employees.
From exchange management shell(run as administrator) use the following commands.
For Global:
Get-Mailbox -Server MAILSERVER | Add-MailboxPermission -User Yourusername -AccessRights Fullaccess -InheritanceType all
Get-Mailbox -Server MAILSERVER | Export-Mailbox -SubjectKeywords “The Subject Line” -StartDate “02/28/2012″ -DeleteContent
For one specific user(rage quit then change your mind after sending?):
Get-Mailbox -Identity targetuser | Add-MailboxPermission -User Yourusername -AccessRights Fullaccess -InheritanceType all
Get-Mailbox -Identity targetuser | Export-Mailbox -SubjectKeywords “The Subject Line” -StartDate “02/28/2012″ -DeleteContent