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MailboxValidator Free Email Checker vs Poptin API

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

APIMailboxValidator Free Email CheckerHEALTHY96Poptin APIREACHABLE100
Uptime · 30d
Uptime · 90d99.44%100%
Uptime · 30d98.3%100%
P50 · ms248698
P95 · ms11381705
AuthapiKeyapiKey
CORSnoyes
HTTPSyesyes
Card requirednono
Commercial useunclearunclear
Data licenseUnverified
Free tierFree tier — API key required
Rate limitUnpublished120 req/window · 119 remaining
In directory since2026-07-052026-10-04
operationalpartialdownno data

MailboxValidator Free Email Checker vs Poptin API: common questions

Which is more reliable, MailboxValidator Free Email Checker or Poptin API?

On our scheduled checks, Poptin API leads on measured uptime — MailboxValidator Free Email Checker at 99.44% versus Poptin API at 100% over 90 days. These are our own probe results, not provider claims; the uptime bars above show the day-by-day record for both.

Which is faster, MailboxValidator Free Email Checker or Poptin API?

MailboxValidator Free Email Checker has the lower median latency in our checks — MailboxValidator Free Email Checker responds in 248 ms versus Poptin API at 698 ms (P50). Tail latency (P95) is in the table above; for most workloads the median is the number that shapes how the API feels.

Do MailboxValidator Free Email Checker and Poptin API need an API key?

Both ask you to authenticate — MailboxValidator Free Email Checker uses an API key and Poptin API uses an API key. Each key is free to obtain; the Auth and Card-required rows above spell out the signup terms.

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

Only Poptin API is browser-friendly — it returns CORS headers over HTTPS. MailboxValidator Free Email Checker needs a server-side call or proxy, so factor that into which one fits a front-end project.

Are MailboxValidator Free Email Checker and Poptin API free for commercial use?

MailboxValidator Free Email Checker has unclear commercial terms, and Poptin API 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.