To create a new Office 365 mailbox, do the following:
- Open up user properties, select the Office 365 tab, expand the desired licensing plan, select an Exchange Online license (or select the entire licensing plan if needed), and click Apply.
- Select Yes or No to create email addresses for all verified domains.
- Select the Mailbox tab and wait for the mailbox properties to load.
- When the buttons are activated, you can perform any additional configuration.