The receivedfor keyword instructs the MTA that if a message is addressed to just one envelope recipient, to include that envelope To: address in the Received: header line it constructs. The keyword receivedfor is the default. The noreceivedfor keyword instructs the MTA to construct Received: header lines without including any envelope addressee information.
The receivedfrom keyword instructs the MTA to include the original envelope From: address when constructing a Received: header line for an incoming message if the MTA has changed the envelope From: address due to, for example, certain sorts of mailing list expansions. receivedfrom is the default. The noreceivedfrom keyword instructs the MTA to construct Received: header lines without including the original envelope From: address.