Which solution worked for you? The Feedback app? If so, did you connect your main Microsoft Account to the 920 during Windows 10 Mobile setup after a hard reset?
I really did not see a "sign in" option on my L920, so this makes no sense.
I found THE solution!!! No resetting or messing around required.
Open outlook settings on phone (the little gear symbol bottom left)
click Accounts
click Add Advanced set-up
click Exchange ActiveSync
follow this:
Server address: s.outlook.com
Domain: <leave empty>
Username: Your email address
Password: Your password
TLS/SSL encryption required: Yes
You secondary outlook account will now sync and your contacts and emails will appear! This is basically the same as the automatic setup you have been trying, but there is a bug with it! Don't forget to Thank me for it
When you installed Win10M did you hard reset? If so, did you sign in with your main Microsoft account? Or did you roll the dice and just move forward with the in place upgrade from WP8.1 without a hard reset?
Did you perform a hard reset after the upgrade? Did the app open and give you a button to "sign in" or something? I found that the app just opened and did nothing to fix the bug for me. That's why I am digging in with you folks to see if there's some reason that it works for some, but not all, phones.
That's actually what I have set on 2 of my 3 Microsoft accounts. The main phone account and the secondary one that I'd been having issues with adding. It's a great feature to have enabled.Login to your primary account from PC, goto "Account Settings-->Security & Privacy-->More Security Settings--> Enable Two Step Verification".
After enabling two step verification, now you can login via Mail app from phone. It worked for me..
Facebook
Twitter
Instagram