OE-Email messages being deleted Automatically After I reply to message

[mixandmatch]

Software USed: Outlook Express

Problem:

When I reply to an e-mail and then close Outlook Express, the message that I replied to is automatically deleted (i.e. when I re-open Outlook express, the message is not there any more!)

I've checked the Delete Folder, and the message is not there either.

Does anyone have any suggestions?
Thanks!