$picture[0] = "image.jpg"; //картинка для вставки в письмо
$to = "mymail@mail.ru"; //кому отправляем письмо
$thm = "Просто письмо"; //тема письма
$body = "test message"; //тело письма (html)

send_mail($to, $thm, $body, $picture);

function send_mail($mail_to, $thema, $html, $path)
  {
    $EOL = "n";
    $boundary     = "--".md5(uniqid(time()));
    $headers    = "MIME-Version: 1.0;$EOL";
    $headers   .= "From: info@mail.ru$EOL";
    $headers   .= "Bcc: mymail@mail.ru$EOL";
    // Вложение отсутствует
    $headers   .= "Content-Type: multipart/related; boundary="$boundary"$EOL";

    $multipart  = "--{$boundary}$EOL";
    $multipart .= "Content-type: text/html; charset=utf-8$EOL";
    $multipart .= "Content-Transfer-Encoding: 8bit$EOL";
    $multipart .= $EOL;
    $multipart .= str_replace("rn", "n", $html);
    $multipart .= $EOL;

    if (!empty($path))
    {
      for($i = 0; $i < count($path); $i++)
      {
        $file = file_get_contents($path[$i]);
        $name = basename($path[$i]);
        $multipart .=  "$EOL--$boundary$EOL";
        $multipart .= "Content-Type: image/jpeg; name="$name"$EOL";
        $multipart .= "Content-Transfer-Encoding: base64$EOL";
        // Вложение отсуствует
        // $multipart .= "Content-Disposition: attachment; filename="$name"$EOL";
        $multipart .= "Content-ID: <".md5($name).">$EOL";
        $multipart .= $EOL;
        $multipart .= chunk_split(base64_encode($file), 76, $EOL);
      }
    }

    $multipart .= "$EOL--$boundary--$EOL";
    //echo $multipart;
    if(!mail($mail_to, $thema, $multipart, $headers))
      return False;
    else
      return True;
    exit;
  }