The problem with POP3 is that it doesn't sync with your mail account in the cloud. So whatever you delete on the Tab doesn't delete on the ISP side (unless you have it set to remove messages from server). So if you delete the POP3 account from the Tab, it will download all the messages on the server side for the amount of days that you set for display, including the ones that you deleted on the phone but not the server.
This is why I moved everything to GMail. If I send an email out of POP3, it's trapped on the phone unless I CC myself. GMail syncs all deletions and sent items to the cloud.