Inbox Check processes north of 100,000 placement checks per day on the free tier. Most users never bump into a rate limit; agencies and platforms that integrate us at scale sometimes do, and there's a paid path when that happens.
What the limits actually are
- Per-email rate limit: 3 tests per 24h rolling window for the same
from. - Per-IP rate limit: 10 tests per 24h rolling window from the same client IP.
- Per-seed rolling cap: 200 inbound test messages per 24h rolling window, per seed mailbox.
- Aggregate throughput: 100K+ tests/day; we'll raise you limits for legitimate use on request.
Rolling windows, not calendar-day resets
Unlike most tools that reset at UTC midnight, our limits are rolling 24h from the last event. This matches how providers actually count — you don't get 200 free test slots at 00:00 UTC and then hit a wall at 23:59. You get a continuous budget that ages out at 24h.
What 100K/day buys you operationally
- Daily placement regression across every outbound template you maintain.
- Per-variant A/B at meaningful sample size.
- Continuous monitoring per domain without batching.
- Agency-scale monitoring across many client domains in parallel.
Need more?
Write in — legitimate use cases (agencies, platforms, research) get lifted limits on request. No plan change required.
FAQ
What happens if I hit a rate limit?
The API returns a 429 with a retry-after header and the expiring timestamp of the oldest request in your window. Your UI shows which providers are temporarily exhausted and hides them from the selector until capacity recovers.
Is there a burst limit?
Per-IP is the burst check. The per-seed and per-email are the flow control.
Do paid plans remove limits?
Paid plans raise them and give priority queuing. There's no 'unlimited' tier because the seed network is finite, but the paid tier covers any reasonable B2B workload.
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