Kickbox vs MailCheck.ai

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.

MailCheck.ai has rebranded to UserCheck, but its original keyless lookup endpoint keeps working unchanged: pass an address and get back disposable, free-provider, MX, and domain-age signals in one JSON response, aimed at blocking throwaway signups. The rebranded product adds a free-to-start paid tier for higher-volume, authenticated use.