A/B testing sends two versions of your email blast to measure which version receives the most engagement from your recipients. The winning version is then sent to the remaining recipients. Integrating testing into your email campaigns ensures that only your best content is delivered to your recipients. This page outlines the process to do A/B tests with your emails.
This page outlines the way to optimize your email deliverability and see high engagement levels in the stats available after you send your email.
Understanding the results of your email blast [NationBuilder Support Site]
This page explains how to connect an Email address to a Broadcaster. Communication between your organization and your community is consolidated around broadcasters. When you attach an email address to a broadcaster, you can send email blasts to your community. By taking a few extra steps in setting up your broadcaster, you can also accept incoming email for a broadcaster.