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MailboxValidator Free Email Checker vs SiteIntel

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

APIMailboxValidator Free Email CheckerHEALTHY96SiteIntelHEALTHY90
Uptime · 30d
Uptime · 90d99.44%100%
Uptime · 30d98.3%100%
P50 · ms248536
P95 · ms11382165
AuthapiKeyapiKey
CORSnono
HTTPSyesyes
Card requirednono
Commercial useunclearunclear
Data licenseUnverifiedUnverified
Free tierFree tier — API key requiredFree tier — key may be required
Rate limitUnpublishedUnpublished
In directory since2026-07-052026-07-05
operationalpartialdownno data

MailboxValidator Free Email Checker vs SiteIntel: common questions

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

On our scheduled checks, SiteIntel leads on measured uptime — MailboxValidator Free Email Checker at 99.44% versus SiteIntel 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 SiteIntel?

MailboxValidator Free Email Checker has the lower median latency in our checks — MailboxValidator Free Email Checker responds in 248 ms versus SiteIntel at 536 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 SiteIntel need an API key?

Both ask you to authenticate — MailboxValidator Free Email Checker uses an API key and SiteIntel 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 SiteIntel from the browser?

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

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

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