I'm having similar issues, for that is seemed to work for me.
From windows insider forum:
Settings -> Add an Account -> Advanced set-up (the last option)
Exchange Active Sync
E-mail address, password as you would expect
Username: <e-mail address>
Doman: <company domain, so xyz.com for example>
serverutlook.office365.com
account name: <e-mail address>
Same problem here. If I restore an update that included that account, then it is there. But then my search also no longer works as it freezes during set up. Starting from scratch, my search works but I can't use my work email on my phone. Both kind of deal breakers unfortunately.
Do your work accounts require encryption? I was unable to get 10149 working last night because of that. I've restored 8.1 and am going to 10149 again without restoring any backups to see if that helps. If not, it's back to 8.1.
Thanks! Actually, it didn't work for me (kept asking me for my password), but with your solution I was able to get inside the app to discover my Outlook w?s added. I just had to turn the sync on
Just tried to add an exchange account via Outlook App -> add an account -> advanced stuff -> ExchangeSyncThing, and...
Oh my ! That worked instantly ! Thank you so much for the tip buddy.