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 %>