Hi Jonathan,
In the DirSync environment, to hide a user from Office 365 address book (GAL), we need to change the user’s msExchHideFromAddressLists attribute to true in local AD. The article you mentioned above lists the attributes that are synced from local AD to Windows Azure Active Directory: support.microsoft.com/.../2256198. We can see the attribute msExchHideFromAddressLists is listed on the table.
By default, we cannot see the Exchange related attributes in AD, if we do not extend the AD schema for Exchange.
To make the attribute msExchHideFromAddressLists appear in local AD, the prerequisite is that the on-premises AD schema is extended for Exchange. To extend the on-premise AD schema, we have a group which is dedicated to handling this kind of issue. To provide you with better service, I suggest you post the question (How to extend AD schema for Exchange) in the TechNet forum:
social.technet.microsoft.com/.../home
Moreover, I can fully understand your concern about extending the AD schema. You can ask them about how to extend the AD schema safely and smoothly.
After the AD schema is extended, we will be able to set the msExchHideFromAddressLists attribute.
In addition, our engineer Neo Yu also provides a workaround in this thread: community.office365.com/.../580817.aspx.
Thanks,
Young Yang