I recently had a computer crash. After re-installing Win XP pro and Outlook 2007, most of the e-mails (but not all) come in with the date attached to the real e-mail address. In order to reply I have to edit off the date.
As an example, the verification e-mail to this website came in as firstname.lastname@example.org Mon Dec 20 03:02:17 2010
I was using XP Pro and Outlook 2007 before the crash and did not have this issue before.