Every email I receive displays the band at the top showing 'Unknown sender' with the options to either 'Delete and block' or to 'Allow sender'.  This is despite all the senders being listed in my 'Contacts' file.  Each time I select to 'Allow sender' but the next email from the same sender again shows 'Unknown sender'

I am using Windows Live Mail 2012 and have recently, finally, managed to update it to the latest build version.  Has anyone any ideas as to what is going wrong this time?