diff --git a/nixos/modules/services/mail/public-inbox.nix b/nixos/modules/services/mail/public-inbox.nix
index 9aa38c4c1c82..4944d46fbd73 100644
--- a/nixos/modules/services/mail/public-inbox.nix
+++ b/nixos/modules/services/mail/public-inbox.nix
@@ -89,7 +89,7 @@ let
       PrivateNetwork = mkDefault (!needNetwork);
       ProcSubset = "pid";
       ProtectClock = true;
-      ProtectHome = mkDefault true;
+      ProtectHome = "tmpfs";
       ProtectHostname = true;
       ProtectKernelLogs = true;
       ProtectProc = "invisible";