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ImprovMX API vs MailCheck.ai

Same instrument, two spec sheets — measured, not claimed.

APIImprovMX APINEW—MailCheck.aiNEW—
Uptime · 30d
Uptime · 90d—%—%
Uptime · 30d—%—%
P50 · ms——
P95 · ms——
AuthapiKeynone
CORSyesyes
HTTPSyesyes
Card requirednono
Commercial useunclearunclear
Data licenseUnverifiedUnverified
Free tierFree tier — API key requiredFree — limits not published
Rate limit301 req/window · 300 remaining · resets 17835265205 req/window · 4 remaining
In directory since2026-07-052026-07-05
operationalpartialdownno data

ImprovMX API vs MailCheck.ai: common questions

Which is more reliable, ImprovMX API or MailCheck.ai?

On our scheduled checks, MailCheck.ai leads on measured uptime — ImprovMX API at —% versus MailCheck.ai at —% over 90 days. These are our own probe results, not provider claims; the uptime bars above show the day-by-day record for both.

Do ImprovMX API and MailCheck.ai need an API key?

MailCheck.ai needs no key, while ImprovMX API requires a free API key. If you want to start calling without signup, reach for MailCheck.ai first.

Can I call ImprovMX API and MailCheck.ai from the browser?

Yes — both ImprovMX API and MailCheck.ai send CORS headers over HTTPS, so front-end code can fetch either directly with no backend proxy. That makes them easy to swap in a client-side app while you compare responses.

Are ImprovMX API and MailCheck.ai free for commercial use?

ImprovMX API has unclear commercial terms, and MailCheck.ai has unclear commercial terms. We track service terms and the data license as separate fields — see the Commercial use and Data license rows above, and confirm both before shipping either in a paid product.