Add additional email addresses to a user in Office 365
Sign in to Office 365.
Go to Admin > Users > Active users.
On the Active users page, do one of the following:
Click or tap to select the user, and then click the email address.
Select the check box next to the user, click Edit Edit, and then click the email addresses tab.
On the Manage email addresses tab, in the text box under Add more email address, type the first part of the new email alias. If you added your own domain to Office 365, you can choose the domain for the new email alias by using the drop-down list.
NOTE: The email address must end with a domain from the drop-down list. If the user needs to receive email sent to an email address in another email service, you should set up email forwarding using the other email service. If you want to add your own domain name to your Office 365 organization, see Get help with Office 365 domains.
Next to the email alias you want to add, click Add.
When you’re done, click Save.
Set as primary email address or remove email address
Sign in to Office 365.
Go to Admin > Users > Active users.
On the Active users page, do one of the following:
Click or tap to select the user, and then click the email address.
Select the check box next to the user, click Edit Edit, and then click the email addresses tab.
On the Manage email addresses tab, do one of the following:
To set an email address as the primary address, select the email address, and click Set as primary . Click OK to confirm that you want to set as primary email address.
To remove an email address, select the email address, and click Delete.
When you are done, click Save.