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FinSignals API vs MailCheck.ai

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

APIFinSignals APINEW—MailCheck.aiNEW—
Uptime · 30d
Uptime · 90d—%—%
Uptime · 30d—%—%
P50 · ms——
P95 · ms——
Authnonenone
CORSyesyes
HTTPSyesyes
Card requirednono
Commercial useunclearunclear
Data licenseUnverifiedUnverified
Free tierFree — limits not publishedFree — limits not published
Rate limitUnpublished5 req/window · 4 remaining
In directory since2026-07-052026-07-05
operationalpartialdownno data

FinSignals API vs MailCheck.ai: common questions

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

On our scheduled checks, MailCheck.ai leads on measured uptime — FinSignals 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 FinSignals API and MailCheck.ai need an API key?

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

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

Yes — both FinSignals 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 FinSignals API and MailCheck.ai free for commercial use?

FinSignals 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.