I also purchased for this sole reason, and docs indicated this is possible.
https://www.shamimsplugins.com/docs/front-end-pm-pro/getting-started-2/only-admin/

However I no longer see “Only admin” but FEP admins, I’m assuming this is the same thing, but with the option for subscribers enabled to send to admin, rather than Admin only.

I’ve implemented the Role-to-Role setting as above which prevents the automatic directory showing of other users on the site, but the “new message” dialog box from the [front-end-pm] shortcode shows the To: field, despite only having one admin.

How do I remove the To: field completely? There is only 1 admin listed for our site.