Yes – you can set up a user who does not have an email address with a custom username – see the image below.
To do this go to the People tab and press the ‘Add a new person’ button. You will see on the page under First Name and Last Name that you must type in a Username that the person will use on log in to their account. This can be an email address but it can also be a custom username as per the example in the image.
* You can then also add an email address for the user that will be used to receive any course, team and message notifications.
If you will not be adding an email address for the new person then you will need to input a password for them to use on their first login, and you will have to notify the user of their login information independently.