從訊息封 To 和 From 位址建構 Received 標頭行

關鍵字：receivedfor、noreceivedfor、receivedfrom 和 noreceivedfrom

receivedfor 關鍵字會指示 MTA，如果郵件只傳送給一位訊息封收件者，則在其建構的Received: 標頭行中包含訊息封 To: 位址。receivedfor 關鍵字為預設。noreceivedfor 關鍵字指示 MTA 建構 Received: 標頭行，但不包含任何訊息封位址資訊。

receivedfrom 關鍵字指示 MTA，如果 MTA 出於某些原因 (例如某種郵件收信人清單擴充) 變更了訊息封 From:位址，則在為內送郵件建構 Received: 標頭行時，包含原始訊息封的 From: 位址。receivedfrom 為預設。noreceivedfor 關鍵字指示 MTA 建構 Received: 標頭行，但不包含原始訊息封 From: 位址。