Disable private messages between members but only between one admin and one member

[Canapin (Coin-coin le Canapin)]

Hallo, es ist nicht nötig, auf einem 8 Jahre alten Thema zu posten, behalten wir die Dinge in deinem ursprünglichen Beitrag

How do I disable personal messages between members, but not admin to members?

How do I disable private messages between members but not admin to members in the latest version?