If you can promote your products in an appealing and informative way, they will probably purchase what you are selling.
Do not send emails to those who have not requested them. Your emails will be considered as spams if you send them to people who are not sign up on their own. This is very bad for business and might even get your IP address blocked by certain Internet providers.
This method of marketing via email gives readers a good value for participating and motivates them to spread the chance to refer friends. Referral programs can be beneficial if you wish to increase your customer base.