composer require phpmailer/phpmailer

<?php
// +----------------------------------------------------------------------
// | ThinkPHP [ WE CAN DO IT JUST THINK ]
// +----------------------------------------------------------------------
// | Copyright (c) 2006-2016 http://thinkphp.cn All rights reserved.
// +----------------------------------------------------------------------
// | Licensed ( http://www.apache.org/licenses/LICENSE-2.0 )
// +----------------------------------------------------------------------
// | Author: 流年 <liu21st@gmail.com>
// +----------------------------------------------------------------------

// 应用公共文件

// 发送邮件
use PHPMailer\PHPMailer\PHPMailer;
use PHPMailer\PHPMailer\Exception;

function mailto($to, $title, $content)
{
    $mail = new PHPMailer(true);
    $mail->SMTPOptions = array(
        'ssl' => array(
            'verify_peer' => false,
            'verify_peer_name' => false,
            'allow_self_signed' => true
        )
    );

    try {
        //Server settings
        $mail->SMTPDebug = 0;                      // Enable verbose debug output
        $mail->CharSet = 'utf-8';
        $mail->isSMTP();                                            // Send using SMTP
        $mail->Host       = 'smtp.163.com';                    // Set the SMTP server to send through
        $mail->SMTPAuth   = true;                                   // Enable SMTP authentication
        $mail->Username   = 'chenyingying1016@163.com';                     // SMTP username
        $mail->Password   = '这里填写授权码';                               // SMTP password
        $mail->SMTPSecure = 'ssl';         // Enable TLS encryption; `PHPMailer::ENCRYPTION_SMTPS` encouraged
        $mail->Port       = 465;                                    // TCP port to connect to, use 465 for `PHPMailer::ENCRYPTION_SMTPS` above

        //Recipients
        $mail->setFrom('chenyingying1016@163.com', 'cyy');
        $mail->addAddress($to);     // Add a recipient

        // Content
        $mail->isHTML(true);                                  // Set email format to HTML
        $mail->Subject = $title;
        $mail->Body    = $content;

        return $mail->send();
    } catch (Exception $e) {
          exception($mail->ErrorInfo, 1001);
    }
}

mailto($data['email'], '注册管理员成功！', '注册管理员成功！');