Kickbox vs Sendinblue

Kickbox's free, keyless Open API endpoint answers a single question — whether an email domain is disposable — a common building block for lightweight signup-form validation. It's a separate, fully free offering from Kickbox's metered full verification product, which is where catch-all (accept-all) detection lives; a live probe found no catch-all surface on the open endpoint at all.

Sendinblue rebranded to Brevo in 2023, and its REST API still covers the same ground under the new name: transactional and marketing email, SMS, and contact/campaign management behind an API-key header. A free plan covers a daily email allowance before metered and subscription paid tiers.