code can go in env file or a file in config

```ruby
   config.action_mailer.delivery_method = :smtp
     config.action_mailer.smtp_settings = {
       address: "smtp.gmail.com",
       port: 587,
       domain: "example.com",
       authentication: "plain",
       enable_starttls_auto: true,
       user_name: ENV["MAIL_USERNAME"],
       password: ENV["MAIL_PASSWORD"]
     }
    config.action_mailer.default_url_options = { host: "localhost:3000" }

```