I have a domain where I want to update the AD schema for Office 365 with the Exchange attributes. During testing this in an test environment I got the error "0x20b Schema update failed: duplicate LDAP display name". The affected attribute is CN=MS-Exch-Extension-Attribute-1,CN=Schema,CN=Configuration,DC=....
Because of this error I looked in the schema context for this attribute (powershell and ADSI editor), to find and maybe disable the attribute. But I cannot find the mentioned attribute.
Has anyone an idea where I can find the attribute or any other hint to solve the error.
Thanks in advance.