Delete all messages after date from mailbox
I was asked to delete everything from a mailbox called familydomains that was older than 2009. Here is the Exchange Powershell command that I used to delete everything earlier than 12/31/2008 to a PST file located in my C:\temp directory.
export-mailbox familydomains -PSTFolderPath C:\temp\ -DeleteContent -endDate 12/31/2008
The advantage to doing it this way is that no emails are actually deleted. They are moved from the mailbox to the PST file, so they can be imported, or viewed through Outlook at a later date if the end user changes their mind.