WordPress更新至6.9会导致邮件发送功能失效，将下面代码添加到主题的function.php即可，如果是子比主题的话更新到最新版本应该就可以了

//WP6.9邮件发送适配start
add_action('phpmailer_init', function($phpmailer) {
// Only fix if using SMTP
if ($phpmailer->Mailer === 'smtp') {
// Set Sender to match From address to satisfy Aliyun SMTP requirements
if (empty($phpmailer->Sender) || $phpmailer->Sender !== $phpmailer->From) {
$phpmailer->Sender = $phpmailer->From;
}
}
}, 10002); // Run after (999) and other plugins
//WP6.9邮件发送适配end