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