AcyMailing Starter is a great marketing tool that allows you to send e-mails to users of the site.
AcyMailing Starter – start your email advertising campaign

The component is a paid version (Enterprise) and free (Starter).
You may use this extension to manage endless number of subscribers, organize them into lists, send messages, and to personalize newsletters and more.
There is a paid counterpart of this component, called RsMail!
The set includes a convenient interface, the excellent interaction with third-party extensions and the ability to copy the message in 1 click.
In addition, you can customize the message as you like – in text format or using HTML markup.
Advantages:
Not required knowledge of HTML, enjoy the creation of advertising messages using visual editor
The process of using the message queue in real time
The subscription module with beautiful effects
Managing the subscription of registered users and site visitors
Record user IP to communicate with the legal right
Validation and proof of mailing
Mass subscription using filters and actions
Automatic user sync Joomla
Import users from any format: CSV, Acajoom, Letterman, Communicator, ccNewsletter, Yanc, jNews
Easy to add article to Joomla newsletter
Quickly to include information about the user (name, e-mail, username…)
Button to share Facebook and Twitter
The display lists on the registration form of Joomla