Outlook asks for O365 mailbox password but the prompt disappears

This vague post is probably not going to help anyone but it’s something I spent 45 mins of my life troubleshooting today and maybe it will help the 1 other person in the world with the same issue and save him/ her some time. :)

A colleague of mine was trying to sign in with an O365 mailbox in his Outlook 2016. Due to the vagaries of our environment he had to sign in as account@tenant.mail.onmicrosoft.com as simply signing as account@domain.com was triggering internal auto-discover and due to how our environment is setup it wasn’t finding the account. Using the longer version forced it to go to Azure AD for authentication but the issue was that he’d get login window (check this blog post for a screenshot), enter the email address account@domain.com (not sure why but account@tenant.mail.onmicrosoft.com didn’t work – because that’s not an Azure AD account I guess?), and whereas usually you’d get the next screen to enter a password in this case it would loop back to the inital page to enter the email address.

Nothing seemed to solve this issue. Of the 45 mins about half an hour was spent trying various suggestions from Google to no avail :) until what finally helped was I suggested adding this account to the default Mail app to see if that helps. Our default Windows 10 build doesn’t the Mail app so we couldn’t do that, so instead I thought let’s add it to the “Email and accounts” in Windows 10 Settings. That worked with no issues (we added the account as account@domain.com) but the good thing is that now when we launch Outlook 2016 and sign in as account@tenant.mail.onmicrosoft.com the login window shows the already signed in account@domain.com and we were able to select that. No more disappearing password window!