There are two different types of pricing structures used by the various email marketing software companies. They are contact based pricing and email based pricing. Contact based pricing charges you on a monthly basis and the price is dependent on the number of email contacts you have uploaded to you account. Email based pricing is either pay-as-you-go or monthly based and is determined by the amount of email credits you wish to purchase. Each email credit allows you to send one email regardless of how many contacts you have uploaded to your account. It is important to note that with monthly email based pricing any email credits you may have remaining at the end of the month will be forfeited.