SMTP Mailer

All output should be run through an escaping function (like esc_html_e() or esc_attr_e()), found '_e'.

$_GET['action'] not unslashed before sanitization. Use wp_unslash() or similar

Hook names invoked by a theme/plugin should start with the theme/plugin prefix. Found: "phpmailer_init".

All output should be run through an escaping function (see the Security sections in the WordPress Developer Handbooks), found '$settings_fields'.

Processing form data without nonce verification.

Detected usage of a non-sanitized input variable: $_POST['from_name']

Detected usage of a possibly undefined superglobal array index: $_REQUEST['_wpnonce']. Check that the array index exists before using it.

load_plugin_textdomain() has been discouraged since WordPress version 4.6. When your plugin is hosted on WordPress.org, you no longer need to manually include this function call for translations under your plugin slug. WordPress will automatically load the translations for you as needed.

Functions declared in the global namespace by a theme/plugin should start with the theme/plugin prefix. Found: "is_smtp_mailer_configured".

Processing form data without nonce verification.

Resource version not set in call to wp_register_style(). This means new versions of the style may not always be loaded due to browser caching.

A function call to __() with texts containing placeholders was found, but was not accompanied by a "translators:" comment on the line above to clarify the meaning of the placeholders.

PHP file should prevent direct access. Add a check like: if ( ! defined( 'ABSPATH' ) ) exit;

Missing "License" in Plugin Header. Please update your Plugin Header with a valid GPLv2 (or later) compatible license.