For now only usecase is collecting newsletter recipients.

Add spree_newsletter to your Gemfile:

gem 'spree_newsletter', github: 'yannickschuchmann/spree_newsletter', branch: '3-0-stable'

Bundle your dependencies and run the installation generator:

bundle
bundle exec rails g spree_newsletter:install

Use this snippet anywhere in your views:

<%= form_for :newsletter_recipient, url: newsletter_recipients_path do |f| %>
  <%= f.label :email %>
  <%= f.text_field :email, placeholder: "Enter your e-mail" %>
  <%= f.submit %>
<% end %>