Losing emails in Outlook 2007

[JeffRome]

We have Outlook 2007 email. My mother thinks she did something when she was fooling around with it. Now every time we get an email, and then read it, and then leave Outlook and return, the email is gone. Not in the inbox (where it should normally be) and not in the other Outlook folders. Nowhere. Again and again. I have used the search function and tried to find the emails but they are gone totally from the computer--not in any folders in or out of outlook. They immediately become deleted permanently. Any idea what she could have done to cause this?