Why are there differences between my tasks in Outlook and Microsoft To-Do?
Microsoft To-Do doesn’t yet support all the varied features of Outlook Tasks. While data you have entered in those additional details in Outlook Tasks will be stored safely on the servers, it will not be displayed in Microsoft To-Do. Specifically, Microsoft To-Do does not currently support the start and end dates, task status, task completion percentage, priority levels, task work hours, task colors, option to format text in notes, or file attachments that are available in Outlook Tasks.
We are currently working to deepen our Outlook integration. Please tell us which options you miss most so that we can prioritize those features with our next updates.