Using New Outlook on Windows for personal email, calendar, and contact management
I am having the same issue as well. Auto email populates as you type it in, but when you Tab out to the CC Line, it changes the TO email address to a Yellow / Gold color, and doesn't allow you to TAB down to other lines. Using your mouse, you can click into the next line. Once at the Subject Line, the TAB key allows you to move to the email body.
Started approx 2-3 days ago. I've tried both Edge and Chrome, with similar effects. However another user in my office, is not having the same issue.