Email marketing is really a good way to promote your business. But be sure that users are relevant with your business. Well its an effective way.

Of course it does. Email marketing provides you a platform for interacting with your customers when you cannot meet them in person. It helps you in understanding their needs and what exactly they are looking for in your website. This in return will help your business because you can then add or subtract accordingly.
Also email marketing is not expensive. So you will actually make profit by this kind of marketing.
What it needs is a copy of the mail, some designing and email ids of your customer base or of any particular desired area.
Hence i guess email marketing is the way to go. Less investment and high returns.

if you have a list that you share and give to your subcribers then yes it does work