NOTE: The below procedure only applies to environments that don't have Exchange on-prem.
  1. Update Schema ---To add the Exchange attributes you have to prepare the on-premises Active Directory schema for Exchange using the Setup.exe /PrepareSchema                             


2.Update in Synchronization Rules Editor--

    1. To add it in the "hide from address lists" capability, open Synchronization Rules Editor, go to Inbound Rules, then find "In from AD - User Common" and click Edit.
    1. Go to Transformations, Add a Transformation with a Direct flow type, a Target Attribute of msExchHideFromAddressLists, and a source of msExchHideFromAddressLists. Save it.

    3.  Update Attribute Value --
    1. Need to change the attribute from FALSE back to TRUE for AAD Sync to detect the delta change.

4. Run AAD Sync to detect the delta change