Chargebee - Chargebee lets you manage subscriptions and payments at scale, handle custom recurring billing scenarios, reduce subscription churn and simplify accounting.
ConvertKit - Email marketing software for online creators. We help you earn a living online through an intuitive email marketing automation tool.
Trexle - Payment Platform Supporting One-time and Recurring Billing
Akismet - Akismet is a spam fighting service that protects millions of WordPress sites from comment and contact form spam.
Killbill - Open-Source Subscription Billing and Payment Platform
Mediaocean - Mediaocean offers the infrastructure to automate the advertising workflow.