Pepipost counts each email sending request for a recipient as one email for credits and billing. For example, if you send one SMTP message to five recipients or include five recipients in your API request, we'll count that as five email credits.
Email requests that end up as Bounces, Drops and Invalids are still requests and thus considered for credit deduction while calculating the credit usage. Hence it is also recommended to keep your system up to date using Webhooks to avoid such overcharges.
Updated about a year ago