You can set the Microsoft Account as your default data file (this puts the calendar on the To-Do Bar) but I do not recommend setting it as the default email account.
If you enabled two-factor authentication on the account, you'll need to generate an app password to use with the account in Outlook.
In this tutorial, I'm adding a Microsoft Account that uses the same email address as a POP3 account in the Outlook profile and setting it as the default data file, so the Calendar and Contacts folders are the default folders. Exchange Active Sync (EAS) was turned off for Outlook desktop clients in February 2017.
(Smartphones can still use it.) Anyone using EAS will need to remove the account from Outlook and add it back using Auto account setup.
Don't forget to move the appointments, contacts, and tasks to the folders first.If you are using a non-Microsoft domain (like Comcast.com, gmail.com, or your own domain name), you'll need to add an alias to your account before you can set it up in Outlook.When the account is hosted on the new servers, it can be added to Outlook as an Exchange account but you'll need to use auto-account setup to set it up.This means if you are viewing the calendar in data file and start a new message, Outlook will use the account to send the message.However, you can edit the registry to mimic the older behavior from Outlook 2007 so you always use default email account as set in File, Account Settings.