app.php

<?php
/**
 * Yii Application Config
 *
 * Edit this file at your own risk!
 *
 * The array returned by this file will get merged with
 * vendor/craftcms/cms/src/config/app.php and app.[web|console].php, when
 * Craft's bootstrap script is defining the configuration for the entire
 * application.
 *
 * You can define custom modules and system components, and even override the
 * built-in system components.
 *
 * If you want to modify the application config for *only* web requests or
 * *only* console requests, create an app.web.php or app.console.php file in
 * your config/ folder, alongside this one.
 */

use craft\helpers\App;

return [
    '*' => [
        'id' => App::env('APP_ID') ?: 'CraftCMS',
        'modules' => [
            'my-module' => \modules\Module::class,
            'site-module' => [
                'class' => \modules\sitemodule\SiteModule::class,
            ],
        ],
        'bootstrap' => ['site-module'],
    ],

    'production' => [
        'components' => [
            // Mailgun
            'mailer' => function() {
                // Get the stored email settings
                $settings = craft\helpers\App::mailSettings();

                // Override the transport adapter class
                $settings->transportType = craft\mailgun\MailgunAdapter::class;

                // Override the transport adapter settings
                $settings->transportSettings = [
                    'domain' => getenv('MAILGUN_DOMAIN'),
                    'apiKey' => getenv('MAILGUN_API_KEY'),
                ];

                // Create a Mailer component config with these settings
                $config = craft\helpers\App::mailerConfig($settings);

                // Instantiate and return it
                return Craft::createObject($config);
            },
        ]
    ],

    'dev' => [
        'components' => [
            // Mailhog in Laravel Homestead
            'mailer' => function() {
                // Get the stored email settings
                $settings = craft\helpers\App::mailSettings();

                // Override the transport adapter class
                $settings->transportType = \craft\mail\transportadapters\Smtp::class;

                // Override the transport adapter settings
                $settings->transportSettings = [
                    'host' => getenv('MAIL_HOST'),
                    'port' => getenv('MAIL_PORT'),
                    'useAuthentication' => false,
                    'username' => getenv('MAIL_USERNAME'),
                    'password' => getenv('MAIL_PASSWORD'),
                ];

                // Create a Mailer component config with these settings
                $config = craft\helpers\App::mailerConfig($settings);

                // Instantiate and return it
                return Craft::createObject($config);
            },
        ]
    ],
];