What is Microsoft To-Do Preview and how does it work?
Microsoft To-Do Preview is a simple and intelligent to-do list app that empowers users to keep track of and focus on the things they need to get done. To-Do Preview uses the Outlook Tasks API to securely sync and store to-dos, so customers can rest easy knowing that their data lives in Exchange and integrates with Outlook Tasks right out of the box. With native support for organization accounts in tenants with Azure Active Directory, To-Do Preview apps support secure login scenarios such as Two-Factor Authentication and a toggle in the O365 admin center for allowing or disallowing organizational access to To-Do Preview apps.
Use of To-Do Preview apps with a work account is subject to a few conditions including preview terms, licensing, organization preferences and pre-requisites. To find specific information on each of those conditions and what to do should the apps provide you or the users you support with an error related to them, please read the following related help articles:
I'm an admin and my organization's users are asking for To-Do licenses
I'm an admin and my organization's users are asking for To-Do to be enabled
I'm an admin and my organization's users are asking for Exchange mailboxes for use with To-Do
Please know that the following account types are not supported:
On-Premise installations of Exchange Server and Microsoft accounts that are not on Exchange Online.
Office 365 Pro Plus, Business, Kiosk K1, Office 365 DE plans and Education accounts.