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MailCheck.ai vs Ntropy Transaction API v1

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

APIMailCheck.aiNEW—Ntropy Transaction API v1NEW—
Uptime · 30d
Uptime · 90d—%—%
Uptime · 30d—%—%
P50 · ms——
P95 · ms——
Authnonenone
CORSyesno
HTTPSyesyes
Card requirednono
Commercial useunclearunclear
Data licenseUnverifiedUnverified
Free tierFree — limits not publishedFree — limits not published
Rate limit5 req/window · 4 remainingUnpublished
In directory since2026-07-052026-07-05
operationalpartialdownno data

MailCheck.ai vs Ntropy Transaction API v1: common questions

Which is more reliable, MailCheck.ai or Ntropy Transaction API v1?

On our scheduled checks, Ntropy Transaction API v1 leads on measured uptime — MailCheck.ai at —% versus Ntropy Transaction API v1 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 MailCheck.ai and Ntropy Transaction API v1 need an API key?

Neither needs a paid key — MailCheck.ai is callable with no signup, and Ntropy Transaction API v1 is callable with no signup. Both are quick to prototype with; rate limits still apply.

Can I call MailCheck.ai and Ntropy Transaction API v1 from the browser?

Only MailCheck.ai is browser-friendly — it returns CORS headers over HTTPS. Ntropy Transaction API v1 needs a server-side call or proxy, so factor that into which one fits a front-end project.

Are MailCheck.ai and Ntropy Transaction API v1 free for commercial use?

MailCheck.ai has unclear commercial terms, and Ntropy Transaction API v1 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.