Office 365, Email, Exchange, Windows, How to grant someone permission to send messages on your behalf

How do I give someone the ability to send messages for me with Exchange and Outlook?

To grant someone permission to send emails on your behalf using Exchange and Outlook, follow these instructions:

Note: If you are using OWA, assigning delegate permissions is not a feature in OWA since you can't open shared calendars as you can in Outlook.

Outlook 365, 2016, 2013