Joomla integration with the Sendy Newsletter software. Sendy is a self-hosted email solution that you pay for just once. It uses Amazon's SES delivery service for incredibly cheap newsletter campaigns at $1 / 10k emails!
The Sendy package adds the following integration:
* Newsletter subscription signup module
* User plugin to auto-subscribe users on registration
* An easy API for adding or removing users to a newsletter from any other extension
Sendy is a great substitute for MailChimp, and uses much cheaper pricing through AWS SES. They have a lot of the same functionality of the MailChimp's paid versions. You also have more access to adapt things to suit your requirements, plus a handy integration to enrol new site members in the lists automatically.