Windows Live Mail 2012 works fine with Windows 10 as long as you DO NOT install the update KB3093594.
This only applies as long any Microsoft Email account you're using has not been upgraded to Outlook Mail. When that happens, you will no longer be able to synchronize the account's mail folders using DeltaSync, and you won't be able to synchronize contacts and calendar with this account, either.
I will stop using then and move to another email service who still retains the correct integration with WLM2012.
There is no other service that offers this three-pronged (mail/contacts/calendar) integration with Windows Live Mail, which was built specifically to synchronize (then) Hotmail (now) Microsoft Email accounts. The best you could hope for is mail synchronization alone via IMAP, which you can also implement in Windows Live Mail.
