Leave a Copy of Email in the Server for POP3

1. Open your Outlook first.
   
2. Go to "Tools" > "Account Settings".
   
3. A dialog box pops up. Double click on the account which you want to change.
   
4. Another window appears. Click "More Settings" button.
   
5. Then go to "Advanced" panel in the following window.
   
6. Check "Leave a copy of messages on the server" like this. Then click "OK".
   
7. Well, you have changed the settings and it will be OK later.