if (m/Reply issued by (.*?):(.*)/) {
  my $issuer = $1;
  my $msg = $2;
  if ($issuer =~ m/([^\\]+)@/) {
    $issuer = $1;
  }
  $msg =~ s/\A\s*'\(ACK\)\s*//;
  $msg =~ s/\s*'\s*\z//;
  # results are in $issuer and $msg
} else {
  # not a Reply issued by message
}