To create a new user with an Exchange Online mailbox, do the following:
- Create a new user account from scratch or copy a template user account.
- Open up user properties, select the Office 365 tab and click Create in Office 365.
- Select Normal User and click OK.
- Assign an Exchange Online license to start the mailbox creation.
- Select the Mailbox tab and wait for the mailbox properties to load.
- When the buttons are activated, you can perform any additional configuration, like calendar delegation.