Office Mac 14.3.8
OSX 10.9 Mavericks

After upgrading to Mavericks a few days ago, Outlook Mac keeps downloading already downloaded messages from Yahoo email account.  Its set up as POP according to the recent changes advised by Yahoo (4-5 weeks ago).

Advanced settings on the account are for mail to be left on the server for 1 week, then deleted (so it can also be downloaded to my iPad and iPhone).

Any ideas??