Properly protect the mailing list directory.

install/ops-install.in

@@ -174,6 +174,8 @@ Phase "sendmail","Configuring sendmail", sub {
 	    DoneIfExists($LIST_DIR);
 	    mkdir($LIST_DIR,0755) or
 		PhaseFail("Unable to create $LIST_DIR: $!");
+	    ExecQuietFatal("$CHGRP mailnull $LIST_DIR");
+	    ExecQuietFatal("$CHMOD 750 $LIST_DIR");
 	};
 	Phase "listfiles", "Creating mailing list files", sub {
 	    foreach my $list (@MAILING_LIST_NAMES) {