DEFAULT = 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:received_protocol {with $received_protocol}}
  ${if def:tls_cipher {($tls_cipher)\n\t}}(Exim $version_number)\n\tid
  $message_id${if def:received_for {\n\tfor $received_for}}

received_header_text = ${if eq {$sender_host_address}{"1.2.3.4"} {"X-Privacy: masked"}{DEFAULT}}