Rate limits & plan limits

Operations

Two kinds of ceilings to be aware of.

Plan limits

Each plan has three hard monthly caps:

Inboxes — maximum active inboxes at any time across your tenant
Emails — maximum sent emails per billing period (inbound is unlimited)
Custom domains — maximum registered custom domains

When you hit one, the relevant endpoint returns 403 with code: "PLAN_LIMIT_REACHED" and a body containing the current and max values. Check your current usage with GET /v1/metrics. Upgrade via the dashboard billing page.

Per-request rate limits

We apply a sliding-window rate limit on /v1/* requests per API key. Typical limit is a few hundred requests per minute — more than enough for agent workloads. If you hit it you'll see 429 Too Many Requests. Back off exponentially and retry.

Send rate

Outbound send has a separate, lower rate governed by your upstream ESP and your domain's warming state. Most agents never notice. If you're trying to push thousands of sends in a tight loop, batch the work across multiple inboxes or spread over time.