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ItsThisForThat vs MailboxValidator Free Email Checker

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

APIItsThisForThatNEW—MailboxValidator Free Email CheckerNEW—
Uptime · 30d
Uptime · 90d—%—%
Uptime · 30d—%—%
P50 · ms——
P95 · ms——
AuthnoneapiKey
CORSnono
HTTPSyesyes
Card requirednono
Commercial useunclearunclear
Data licenseUnverifiedUnverified
Free tierFree — limits not publishedFree tier — API key required
Rate limitUnpublished (docs ask you not to hammer it)Unpublished
In directory since2026-07-052026-07-05
operationalpartialdownno data

ItsThisForThat vs MailboxValidator Free Email Checker: common questions

Which is more reliable, ItsThisForThat or MailboxValidator Free Email Checker?

On our scheduled checks, MailboxValidator Free Email Checker leads on measured uptime — ItsThisForThat at —% versus MailboxValidator Free Email Checker 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 ItsThisForThat and MailboxValidator Free Email Checker need an API key?

ItsThisForThat needs no key, while MailboxValidator Free Email Checker requires a free API key. If you want to start calling without signup, reach for ItsThisForThat first.

Can I call ItsThisForThat and MailboxValidator Free Email Checker from the browser?

Neither sends browser-friendly CORS headers reliably, so call ItsThisForThat and MailboxValidator Free Email Checker from a server or proxy rather than client-side. The CORS and HTTPS rows above show exactly what we detected for each.

Are ItsThisForThat and MailboxValidator Free Email Checker free for commercial use?

ItsThisForThat has unclear commercial terms, and MailboxValidator Free Email Checker 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.