I've been browsing for the right solution, but I can't find a proper explanation. I have a user with an email address and licenses; I would like to add 2nd and 3rd email addresses to this user. The user should be able to send and receive emails and outlook calendar items using this email address. I have tried doing this using aliases but then when the user sends an email it states that the user is 'sending it on behalf of'. What is the best practice of assigning multiple email addresses to one user without having to create a user in Office 365??