The main user management page of office 365 is very simple and easy to use. However, you may have noticed that it has a pretty serious shortage of options and settings. A common task is to add multiple email addresses to be directed at a single office 365 user, but it isn’t obvious right off the bat how to do this.
Note, that this method does not work in a Federated or DirSynced environment as the changes must be made in the local Active Directory.
Sign into https://portal.microsoftonline.com as an administrator. At the top of the page, click on the “Admin” tab to enter the main administration page.
Click this “manage” button and it will take you to a new management page. Here you should already be on the correct page – “Users and Groups” should be the tab selected on the left, and “Mailboxes” should be the tab selected on top. From here, click on the user you would like to add more email addresses to and then click “details”. You will come across this page.
From here, click on “Email options”. It will give you a box that allows you to add, edit, and remove secondary SMTP addresses. You’ve probably already guessed this by now, but to add a secondary address, click on “add” and type in the username you want, then select the domain from the dropdown menu. You are of course only allowed to choose from domains you already have attached to your office 365 account.
Once you are done hit the “save” button at the bottom. Any emails you send will still come from your primary account, but any emails sent to your secondary email address will arrive in your exchange mailbox. Because these are not separate office 365 users/mailboxes, you can add as many as you’d like. Enjoy!