Plans based on the number of contacts you have
This type of plan is ideal if you frequently send emails (or a newsletter) to your list of contacts.
Plans based on the number of emails you need to send
Pay based on the amount of email you need to send. This is ideal if you send only one newsletter per month.
Pay per email (email credits)
If you rarely or sporadically need to send emails this will be the best fit for you. One credit allows you to send one email.