Our Active Directory is synced to Exchange Online using AD Connect.
After renaming a user I have noticed the Alias field in Exchange Online remains unchanged.
Changing it online fails with this message:
The operation on mailbox "John.Smith" failed because it's out of the current user's write scope. The action 'Set-Mailbox', 'Alias,EmailAddresses', can't be performed on the object 'John Smith' because the object is being synchronized from your on-premises organization. This action should be performed on the object in your on-premises organization.
In AD, there is no where I am able to change it. I have found solutions that state I should change the mailNickName attribute, but this does not appear in the Attribute Editor.
So I followed method 2 of this guide and modified the powershell to be this:
Get-ADUser -Properties * -Filter {name -like "John.Smith"} | set-aduser -replace @{mailnickname="John.Smith"}
Then I ran AD Connect delta sync. But it does nothing, the original Alias is still there.
Best Answer
Please double check in ADSI. Or did you find proxyaddress, please try to change this, the ProxyAddresses attribute is where the aliases are stored.
Did you ever install Exchange on-premises server in this environment? If not, you could extend Active Directory schema to include Exchange attributes:
http://guides.appriver.com/m/89074/l/698027-extend-active-directory-schema-to-include-exchange-attributes