phpmailer发送两封邮件

Question

I Have a form, which let users register for a guestlist. After this they are getting a confirmation Mail. when my form is used, the phpmailer sends 2 mails to the receiver. this script is included after the verification is done. Can you tell me what is wrong?

<?php

//create connection
require_once 'connection.php';

/* ===================
variables
====================== */
$lastname = $_POST['lastname'];
$firstname = $_POST['firstname'];
$email = $_POST['email'];


/* ===================
sql data query
====================== */
//set query checking for duplicate entries
$nameQuery = "SELECT * FROM guestlist WHERE lastname LIKE '$lastname' AND firstname LIKE '$firstname' AND email LIKE '$email'";


//send checking query to database
$getName = mysqli_query($connection, $nameQuery)
        or die ("fehlgeschlagen" .mysqli_connect_error());


//get result from database request
$resultGetName = mysqli_fetch_array($getName);


/* ===================
html message
====================== */
$mailSubjectInput = 'Confirmation';

$mailBodyInput = 'This is a Testmail';

/* ===================
mail function
====================== */
//PHPMailer setup
require_once 'libs/PHPMailer/PHPMailerAutoload.php';

$mail = new PHPMailer;

$mail->isSMTP();
$mail->SMTPAuth = true;
//$mail->SMTPDebug = 2; -- display dev/error messages

$mail->Host = $mailHost;
$mail->Username = $mailUser;
$mail->Password = $mailPW;
$mail->SMTPSecure = 'TLS';
$mail->Port = 25;


$mail->From = $mailSender;
$mail->FromName = $mailSenderName;
$mail->addReplyTo($mailSender, $mailSenderName);
$mail->addAddress($email, $firstname .' ' .$lastname);


// input
$mailSubject = utf8_decode($mailSubjectInput);
$mailContent = utf8_decode($mailBodyInput);

$mail->Subject = $mailSubject;
$mail->Body = $mailContent;
$mail->AltBody = $mailContent;

//var_dump($mail->send()); -- test if connection is true/false
$mail->send();