1. Set Author role from “Subscriber” to “Contributor”
Most Directory Listing authors are assigned as “Subscriber”, unless purposely set to higher role.

To distinguish these authors from other non-publishing subscribers, set their role to “Contributor” (so far no authors are assigned as Contributor).

Without this step, all authors will be set up “no role” in step 2. And it will be difficult and time consuming to recover.

2. Set “Subscriber” to “no role”
Now all “Subscriber” are users who have not published Listings. They can be all downgraded to “no role”.

If needed, there are plugins to block (batch) set users from one role to another (in this case “no role”).

3. Set “Contributor” (the authors of Directory Listing) back to ‘Subscriber”.
“no role” user cannot access backend admin console, if in the future, there is need for existing author to do anything, Subscriber is the minimum User Role to access Directory. So change those authors role from previously set “Contributor” back to “Subscriber”.

4. Notify existing Subscriber (now only authors are Subscriber) to use FBU email account
By downgrading user role to “no role”, existing Listings won’t be affected. All listings are still available to the public on the frontend, and available for editing in the backend by Editor / Admin.