Brand new PC, W10 Pro, Core i5, 8gb ram, 1tb Disk. Logged onto portal.office365.com and downloaded the Office applications from an Office 365 E3 account. Started Outlook 2016, added two profiles: info and personal. I then chose for it to ask me which profile to use when I opened Outlook. For the info profile the password is known, several people in the office can use it. For this account remembering the password is fine. For the personal account this holds staff information and other details, only the manager can see this. The 'Remember password' is never ticked. When I go into Outlook and choose the personal profile it shows me the 'Enter password' screen. If I just sit there and type nothing, or press cancel it will still take me into the email account and allow me to send and receive emails.
The account used to download the software is the Manager's account. Is that where it's getting the password from? Given that I've never entered it I can't see how it is allowing entry into the email, let alone why pressing 'cancel' takes you in.
I have tried disconnecting the account but it makes no difference. I have tried deleting all credentials mentioning that account, no difference.
In some scenarios, Outlook will auto-log you using the credentials of the current windows (AD) user. In general, you should not be using it in a "shared PC" scenario, as the program is simply not designed to run in such. Perhaps using OWA will be a better option?