Managing personal Outlook.com account settings, security, and privacy
I too tried posting about this problem in UserVoice. I received a similar reply (in an email) as Cherche did ... Here is what I received ...
Thank you for providing feedback on the new Outlook on the web experience. This is our new Outlook and the ability to go back to the previous format is not available.
Again, let me state that this auto-complete problem has nothing to do with the new Outlook Mail system ... this problem has nothing to do with browser settings ... this problem is being caused by a bug in the new Microsoft Account sign on page.
Forum Moderators: if you really want to help ... then reproduce this problem on your own: in your browser, search for "outlook.com". When the sign on page opens, try entering the first few characters of your ID into the input box. You will see that auto-complete is not working. Then escalate this problem to Microsoft.