SMTP Test in WordPress Dashboard

functions.php

add_action('admin_menu', 'smtp_test_email_menu');

function smtp_test_email_menu() {
    add_menu_page(
        'SMTP Test Email', // Page title
        'SMTP Test Email', // Menu title
        'manage_options',  // Capability
        'smtp-test-email', // Menu slug
        'smtp_test_email_page' // Callback function
    );
}

function smtp_test_email_page() {
    ?>
    <div class="wrap">
        <h1>Send Test Email</h1>
        <?php
        if (isset($_POST['send_test_email'])) {
            $to = sanitize_email($_POST['to_email']);
            $subject = 'SMTP Configuration Test';
            $message = 'Hello,

This is a test email to confirm that your WordPress site is configured correctly to send emails using Gmail SMTP.

Best regards,
Your WordPress Site';

            if (wp_mail($to, $subject, $message)) {
                echo '<div class="notice notice-success"><p>Email sent successfully!</p></div>';
            } else {
                echo '<div class="notice notice-error"><p>Failed to send email.</p></div>';
            }
        }
        ?>
        <form method="post">
            <table class="form-table">
                <tr valign="top">
                    <th scope="row">Recipient Email</th>
                    <td><input type="email" name="to_email" required /></td>
                </tr>
            </table>
            <?php submit_button('Send Test Email', 'primary', 'send_test_email'); ?>
        </form>
    </div>
    <?php
}