HostGator服务器上PHPMailer+Gmail SMTP发送成功却收不到邮件问题

我使用PHPMailer结合Gmail SMTP服务器搭建了contact_us表单，本地环境运行完全正常，但部署到HostGator服务器后，页面提示“邮件发送成功”，但作为收件人的Gmail账户却未收到邮件。我仅能访问服务器上上传站点文件的根目录，相关代码如下：

require "vendor/autoload.php";

// Include packages and files for PHPMailer and SMTP protocol

use PHPMailer\PHPMailer\PHPMailer;
use PHPMailer\PHPMailer\Exception;

require 'vendor/phpmailer/phpmailer/src/Exception.php';
require 'vendor/phpmailer/phpmailer/src/PHPMailer.php';
require 'vendor/phpmailer/phpmailer/src/SMTP.php';

// Initialize PHP mailer, configure to use SMTP protocol and add credentials

$mail = new PHPMailer();
$mail->IsSMTP();
$mail->Mailer = "smtp";

$mail->SMTPDebug  = 0;
$mail->SMTPAuth   = TRUE;
$mail->SMTPSecure = "tls";
$mail->Port       = 587;
$mail->Host       = "smtp.gmail.com";
require_once 'folder/video.php';
$mail->Username = SMTP_USERNAME;
$mail->Password = SMTP_PASSWORD;

$success = "";
$error = "";
$name = $message = $email = "";
$errors = array('name' => '', 'email' => '', 'message' => '');

if (isset($_POST["submit"])) {
    if (empty(trim($_POST["name"]))) {
        $errors['name'] = "Your name is required";
    } else {
        $name = SanitizeString($_POST["name"]);
        if (!preg_match('/^[a-zA-Z\s]{2,50}$/', $name)) {
            $errors['name'] = "Only letters and spaces allowed";
        }
    }

    if (empty(trim($_POST["email"]))) {
        $errors["email"] = "Your email is required";
    } else {
        $email = SanitizeString($_POST["email"]);
        if (!filter_var($email, FILTER_VALIDATE_EMAIL)) {
            $errors["email"] = "Please give a proper email address";
        }
    }

    if (empty(trim($_POST["message"]))) {
        $errors["message"] = "Please type your message";
    } else {
        $message = SanitizeString($_POST["message"]);
        if (!preg_match("/^[a-zA-Z\d\s]+$/", $message)) {
            $errors["message"] = "Only letters, spaces and maybe numbers allowed";
        }
    }

    if (array_filter($errors)) {
    } else {
        try {

            $mail->setFrom($email, $name);

            $mail->addAddress("mail@gmail.com", "My name");

            $mail->Subject = 'new message';

            $mail->Body = $message;

            // send mail

            $mail->send();

            // empty users input

            $name = $message = $email = "";

            $success = "Message sent successfully";
        } catch (Exception $e) {

            // echo $e->errorMessage(); use for testing & debugging purposes
            $error = "Sorry message could not send, try again";
        } catch (Exception $e) {

            // echo $e->getMessage(); use for testing & debugging purposes
            $error = "Sorry message could not send, try again";
        }
    }
}

function SanitizeString($var)
{
    $var = strip_tags($var);
    $var = htmlentities($var);
    return stripslashes($var);
}

表单在本地环境运行正常，以下为服务器文件夹截图和本地VSCode文件夹截图：

内容的提问来源于stack exchange，提问作者Teleport