&`I `& local interface used
&`K `& CHUNKING extension used
&`id `& message id for incoming message
+&`M8S `& 8BITMIME status for incoming message
&`P `& on &`<=`& lines: protocol used
&` `& on &`=>`& and &`**`& lines: return path
&`PRDR`& PRDR extension used