Outlook Issue

["Joe Pluta" <joepluta@xxxxxxxxxxxxxxxxx>]

This is a VERY vague question, third party through my wife, so if you're
answer is "I need more information", please let me know what info you
need and I'll see if I can get it.

This is the scenario: a user receives an email message in Outlook.  It
shows up in his Inbox.  The user replies to the email, and the reply is
sent normally, but the original email "disappears".  I'm not sure
whether that means it gets moved to the deleted folder, some other
folder, or is deleted from the box entirely.  But in any case, it's no
longer in the Inbox.

Has anybody heard of this sort of behavior?  Some setting perhaps in
Outlook that causes a message to be moved once it is replied to?

Joe