PHP スクリプトで電子メールの存在を確認できますか?

<?php

function verifyEmail($email_address) {
    // Set up sender email
    $sender_email = 'your_email@example.com';

    // Create a unique identifier for this verification
    $verification_token = md5(uniqid());

    // Set up headers
    $headers = "From: $sender_email\r\n";
    $headers .= "Reply-To: $sender_email\r\n";
    $headers .= "Return-Path: $sender_email\r\n";
    $headers .= "Message-ID: <" . time() . "TheSystem@" . $_SERVER['SERVER_NAME'] . ">\r\n";
    $headers .= "X-Mailer: PHP/" . phpversion() . "\r\n";
    $headers .= "MIME-Version: 1.0\r\n";
    $headers .= "Content-Type: text/plain; charset=iso-8859-1\r\n";

    // Try sending an email
    if (mail($email_address, "Email Verification", "This is a test message.", $headers)) {
        echo "Email sent successfully. Waiting for confirmation...\n";

        // Wait for a while to receive a bounce-back email
        sleep(5);

        // Check if the verification token is returned in the bounce-back email
        $bounce_back_email = "bounce_back_$verification_token@$sender_email";
        $bounce_back_message = shell_exec("grep -l $verification_token /var/mail/$bounce_back_email");

        if ($bounce_back_message !== false) {
            echo "The email address '$email_address' exists.\n";
            // Clean up bounce-back email
            shell_exec("rm /var/mail/$bounce_back_email");
            return true;
        } else {
            echo "The email address '$email_address' does not exist or could not be verified.\n";
            return false;
        }
    } else {
        echo "Failed to send email.\n";
        return false;
    }
}

// Usage example
$email_to_verify = "[email protected]";
verifyEmail($email_to_verify);

?>