Config: add action_mailer.asset_host var to send image in email

config/environments/development.rb

@@ -42,6 +42,7 @@ Rails.application.configure do
   # Action Mailer settings
   config.action_mailer.delivery_method = :smtp
   config.action_mailer.default_url_options = { host: 'localhost', port: 3000 }
+  config.action_mailer.asset_host = 'http://localhost:3000'
   # Config for mailcatcher https://mailcatcher.me/
   config.action_mailer.smtp_settings = {
     :address => "localhost",