Had the same issue after a 'helpful' windows 10 update. I wish they tested updates before shipping them out!!!
I found wldcore.dll in an older folder and had to copy it to lots of places before I found the right one. Windows live/mail .. windows mail both in programs and programs(86). Cant remember which was the last one ( I think windows mail) but it now works and I haven't lost the accounts. I did try reloading windows live and of course it didn't work.