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• QmailSpfPatch added by Ed Li <zixia@zixia.net>
  Qmail always save envelope-from in Return-Path header, buf if: 1. We must forward mail to another server, and use SpamAssassin in that server(Return-Path may be changed); 2. any poor guy like me: can't make Return-Path work with SPF(with SpamAssassin 3.0.0-r20550); We need this patch .
  
• Exim 4
  Exim 4 can be configured to output the envelope-sender by adding a custom received_header_text option. The following adds the envelope-sender to the default received header template:
  

received_header_text = Received: \
      ${if def:sender_rcvhost {from $sender_rcvhost\n\t}\
      {${if def:sender_ident {from $sender_ident }}\
      ${if def:sender_helo_name {(helo=$sender_helo_name)\n\t}} }}\
      by $primary_hostname \
      ${if def:sender_address {(envelope-from\n\t\
      <$sender_address>)\n\t}}\
      ${if def:received_protocol {with $received_protocol}} \
      ${if def:tls_cipher {($tls_cipher)\n\t}}\
      (Exim $version_number)\n\t\
      id $message_id\
      ${if def:received_for {\n\tfor $received_for}}

Comments

Actually, the Return-Path is standard now, and I don't see any need to add yet another way to specify the envelope recipient. Go read RFC-2821 section 4.4 where this header is defined as a MUST. – Arik Baratz

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