If your phone's mail app doesn't natively support Modern Authentication, it is time to replace it.

nztim:

If your phone's mail app doesn't natively support Modern Authentication, it is time to replace it.

For Calendar: open Outlook, click the cogwheel, scroll down to Calendar, click Sync Calendar.

You only need this if you really, really want to use the native Calendar app. There's no reason to. Use the Outlook Calendar. Unless you have a Gmail/Workspace account with Calendar too and you want all in one place.

For Contacts: open Outlook, click the cogwheel, scroll down to Contacts, click Sync Contacts.

You certainly want this if you want your Outlook/Exchange contacts synchronise to phone Contacts so you can have their names appear in Call, Messages, etc.