I have owned a MacBook Pro loaded with MS Outlook 2011 for Mac for almost a year now.  I use Outlook for my personal Yahoo email but, leave the emails on the server since I also an iPhone and internet sometimes to manage my personal emails.  About three months ago, Outlook began downloading all of my old emails from the Yahoo server again.  I thought this might have been a one time deal due to daylight savings time change, etc. but, this has now occurred three times (seems to be at the beginning of a new month).  Any recommendations on how to resolve?  Thanks.