Index: share/authentication_milter.json
--- share/authentication_milter.json.orig
+++ share/authentication_milter.json
@@ -6,8 +6,8 @@
 
     "connection"             : "inet:12345@localhost",
     "umask"                  : "0000",
-    "runas"                  : "nobody",
-    "rungroup"               : "nogroup",
+    "runas"                  : "_milter-auth",
+    "rungroup"               : "_milter-auth",
     "chroot"                 : "",
 
     "listen_backlog"         : 20,
