Helo

Helo is an email API built for developers and platforms that send on behalf of their customers. Contain bad senders before they drag down deliverability, let customers send from their own domains, and keep stats, unsubscribes, and credentials separate per tenant. It also covers the fundamentals: REST API and SMTP, SDKs in popular languages, separate transactional and broadcast infrastructure, and usage-based pricing starting at just $0.00035 per email—all features included.