Mailchimp is an Email Marketing system which I have been using since November 2013. The Entrepreneur package allows 2000 subscribers and up to 12000 emails and is free of charge. As an example, you would need to send out 23 emails every week for 10 years before reaching the 12000 limit! So if you can keep your subscribers list under 2000 this is a very good package indeed.
You can create templates so your mailings will always go out with the same format and appearance which gives your business a more professional look. And you can create categories within your list of subscribers so you can send mailings out to just a small section of them.
You can also create opt-in forms for your website which allows your customers to subscribe to your newsletters automatically without extra input from you.