No, we do not charge based on the number of sent emails or the number of contacts (subscribers).
How many contacts I can add to your system.
You can add as many as contact and send as many emails you want to send.
Although the daily sending limit will apply based on your selected server setup plan.
Basic Setup - 25k emails/day
Advance setup - 200k emails/day
Custome Setup - 1 Million emails/day