Fix for The operation on mailbox "" failed because it’s out of the current user’s write scope. The action ‘Set-Mailbox’, ‘HiddenFromAddressListsEnabled’, can’t be performed on the object

Mailboxes in Exchange Online can’t be set as hidden in the address book, while having DirSync / ADConnect enabled to sync your on premises AD objects. In fact, when trying to do so in the Exchange Online web interface, the following error will popup:

The operation on mailbox “” failed because it’s out of the current user’s write scope. The action ‘Set-Mailbox’, ‘HiddenFromAddressListsEnabled’, can’t be performed on the object ” because the object is being synchronized from your on-premises organization. This action should be performed on the object in your on-premises organization.

To (un)hide the mailbox from your address book, you need to modify the msExchHideFromAddressLists attribute on the related Active Directory object. To fulfill, follow these steps

1. Logon to a server on which Exchange Management Console is installed
2. Open Active Directory Users and Computers (dsa.msc)
3. Click View–> Advanced Features  This enables the tab Attribute Editor
4. Navigate to the User / AD Account you want to (un)hide in your address book. Double Click to open its properties
5. Go to tab Attribute Editor
6. Scroll down to msExchHideFromAddressLists
7. Double click and choose True or False. Not Set will be the default which is normally False
8. Click OK twice. Wait or force a sync with Azure to reflect your changes.