Confirmation email

Question

Good afternoon, I recently entered an email confirmation system for users who are signing up and it is working perfectly, however I want the users already registered confirm tbm but when I tried to use the msm system I did not succeed... alg can take a look?

<?php    
    $email = $_POST['email'];
    $email2 = $_POST['email'];
    $user = $_POST['user'];

    $servidor = "localhost";
    $usuario = "root";
    $senha = "";
    $dbname = "teste";

    //Criar a conexao
    $conn = mysqli_connect($servidor, $usuario, $senha, $dbname);

    $result_leados = "INSERT INTO leados (email) VALUES ('$email')";
    $resultado_leados = mysqli_query($conn, $result_leados);

    $leado_id = mysqli_insert_id($conn);

    $valor_chave = md5(date('Y-m-d H:i'));

    $link = "http://localhost/Mail/baixar.php?chave=".$valor_chave;

    $result_links_emaos = "INSERT INTO links_emaos (link, leado_id) VALUES ('$valor_chave', '$leado_id')";
    $resultado_links_emaos = mysqli_query($conn, $result_links_emaos);