What Gary said.
Question: Did you import the contents of your old computer's OE Sent Items
folder into Windows Mail?
General Windows Mail User-Caveats:
- Don't use Inbox or Sent Items to archive messages. Move them to local
folders created for this purpose.
- Empty Deleted Items folder daily.
- Do not cancel Automatic Compacting, should it occur, and do not attempt to
close Windows Mail via Task Manager or shutdown your machine if Automatic
Compacting is taking place.
- Disable email scanning by your anti-virus application. It can cause
corruption (i.e., loss of messages) and provides no additional protection:
Why you don't need your anti-virus to scan your email
http://thundercloud.net/infoave/tutorials/email-scanning/index.htm