如何用PHP结合GMAIL SMTP发邮件？PHPMailer SSL证书验证失败求助

在XAMPP本地环境使用PHPMailer发送Gmail邮件时出现SSL证书验证失败错误，此前通过XAMPP的sendmail功能可正常发送。具体错误信息如下：

SMTP Error: Could not connect to SMTP host. Connection failed. stream_socket_enable_crypto(): SSL operation failed with code 1. OpenSSL Error messages:error:1416F086:SSL routines:tls_process_server_certificate:certificate verify failed. Message could not be sent. Mailer Error: SMTP Error: Could not connect to SMTP host. Connection failed. stream_socket_enable_crypto(): SSL operation failed with code 1. OpenSSL Error messages: error:1416F086:SSL routines:tls_process_server_certificate:certificate verify failed.

使用的代码如下：

<?php
//Import PHPMailer classes into the global namespace
//These must be at the top of your script, not inside a function
use PHPMailer\PHPMailer\PHPMailer;
use PHPMailer\PHPMailer\SMTP;
use PHPMailer\PHPMailer\Exception;

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

//Create an instance; passing `true` enables exceptions
$mail = new PHPMailer(true);

try {
    //Server settings
    $mail->SMTPDebug = SMTP::DEBUG_SERVER;                      //Enable verbose debug output
    $mail->isSMTP();                                            //Send using SMTP
    $mail->Host       = 'smtp.gmail.com';                     //Set the SMTP server to send through
    $mail->SMTPAuth   = true;                                   //Enable SMTP authentication
    $mail->Username   = 'myemail@gmail.com';                     //SMTP username
    $mail->Password   = 'mypassword';                               //SMTP password
    $mail->SMTPSecure = 'tls';            //Enable implicit TLS encryption
    $mail->Port       = 587;                                    //TCP port to connect to; use 587 if you have set `SMTPSecure = PHPMailer::ENCRYPTION_STARTTLS`

//Recipients
    $mail->setFrom('myemail@gmail.com', 'Mailer');
    $mail->addAddress('myemail@gmail.com', 'Joe User');     //Add a recipient

//Content
    $mail->isHTML(true);                                  //Set email format to HTML
    $mail->Subject = 'Here is the subject';
    $mail->Body    = 'This is the HTML message body <b>in bold!</b>';
    $mail->AltBody = 'This is the body in plain text for non-HTML mail clients';

    $mail->send();
    echo 'Message has been sent';
} catch (Exception $e) {
    echo "Message could not be sent. Mailer Error: {$mail->ErrorInfo}";
}

1. 修复Gmail身份验证方式 #

Gmail已不再支持普通密码登录SMTP，必须使用应用专用密码或OAuth2验证：

• 若开启两步验证，直接生成应用专用密码替换代码中的mypassword
• 未开启两步验证的用户，需先开启该功能，再生成应用专用密码

2. 解决SSL证书验证问题 #

XAMPP自带的OpenSSL可能缺少根证书，可通过以下两种方式处理：

方式一：配置CA证书路径 #

下载Mozilla官方根证书包（cacert.pem），将其放置到XAMPP目录下（如xampp/php/extras/ssl/），然后修改php.ini文件：

openssl.cafile = "C:/xampp/php/extras/ssl/cacert.pem"
curl.cainfo = "C:/xampp/php/extras/ssl/cacert.pem"

修改完成后重启XAMPP的Apache服务。

方式二：临时禁用证书验证（仅测试环境使用，生产环境不推荐） #

在PHPMailer的服务器设置代码块中添加以下配置：

$mail->SMTPOptions = array(
    'ssl' => array(
        'verify_peer' => false,
        'verify_peer_name' => false,
        'allow_self_signed' => true
    )
);

3. 修正SMTPSecure配置 #

代码注释已说明端口587对应PHPMailer::ENCRYPTION_STARTTLS，建议将字符串配置改为常量引用，避免拼写问题：

$mail->SMTPSecure = PHPMailer::ENCRYPTION_STARTTLS;

内容的提问来源于stack exchange，提问作者123 456