Scenario: A federated Office 365 user's Alias is incorrect.  You wish to change it, but changing the proxyAddress or Mail attribute in Active Directory does not update the Alias.

Before this tutorial, you can see the Alias has a typo in it (the m and o are out of place)

After completing this tutorial, we will update the Alias to look correct

Solution: Complete the following steps below to update the Alias

1. Login to one of your Domain Controllers and open up Active Directory Users and Computers
   
   
2. Find the user that owns the mailbox, right click on them, and select Properties
   
   
3. Select the Attribute Editor Tab and find the mailNickname attribute
   
   1. Note: You will need to Enable Advanced Features on Active Directory Users and Computers to see this tab
      
4. Type in the desired value you wish to show up in the Alias field on the Office 365 Exchange Portal and click OK
   
5. Click Apply on the Active Directory Users and Computers dialog
   
6. Wait for the Office 365 Directory Synchronization tool runs and updates the users online
   1. Note: Tutorial on how to do this can be found here: http://jackstromberg.com/2012/08/force-directory-synchronization-with-office-365/
7. Ensure that the Alias field has updated in the Exchange Administrative portal