Account billing is based on the number of Active Subscribers in your account. These include all of the subscribers who have the “active” status and not others such as “unsubscribed” or “bounced.” If you send an email to a subscriber, it will count toward your plan’s sending limit. For example, if you have a plan with a sending limit of 2500, then you can send emails to up to 2500 unique subscribers within a 30-day period. These subscribers still count towards your limit even if they are deleted from your account after you have sent them an email. They will no longer be counted toward your limit 30 days after the last email was sent to them.