1. Open Microsoft Outlook 2010
  2. Click on the File Tab and then on Account Settings
  3. Again click on Account Settings
  4. Click on the Email account on which you want to check it
  5. Click on Change
  6. Click on More Settings
  7. Click on the Advanced Tab
  8. Under the Delivery Section make sure the checkbox next to “Leave a copy of message on the server.” has been unchecked

NOTE: Insure you connect via POP and not IMAP