add_action( 'phpmailer_init', array( &$this, 'prefix_send_smtp_email' ) , 10 );

public function prefix_send_smtp_email( PHPMailer $phpmailer ) {

    // Define that we are sending with SMTP
    $phpmailer->isSMTP();

    // The hostname of the mail server
    $phpmailer->Host = "mail.gandi.net";

    // Use SMTP authentication (true|false)
    $phpmailer->SMTPAuth = true;

    // SMTP port number - likely to be 25, 465 or 587
    $phpmailer->Port = "587";

    // Username to use for SMTP authentication
    $phpmailer->Username = "contact@confdays.com";

    // Password to use for SMTP authentication
    $phpmailer->Password = "xxxxxxxx";

    // Encryption system to use - ssl or tls
    $phpmailer->SMTPSecure = "tls";

    $phpmailer->From = "contact@xxx.com";
    $phpmailer->FromName = "Jhon Do";
}