Rate limits & suppression

Send budgets

Each send is checked against a per-minute burst window and a rolling 24-hour daily cap. Both are derived from your plan: the daily cap is the plan's email allowance, and the burst is 1% of it (floor 10/min).

The two windows are checked together and atomically: a rejected request consumes no budget in either window, so a client hammering into a 429 can never drain its daily quota. Organizations placed in a throttled state run on a reduced fraction (default 10%) of these numbers.

Platform limits

The non-sending /v1 surface — domains, mailboxes, audiences, broadcasts, templates, webhooks, analytics — is metered per API key rather than per plan:

The two run on separate windows, so polling a domain verification or a broadcast's progress cannot starve a write. Rejections carry the same Retry-After header as send budgets.

A handful of endpoints add their own guard on top — re-checking one domain's DNS, for instance, is limited to once per 30 seconds regardless of the key's remaining budget.

Handling 429

When a window is exhausted the request returns 429 rate_limited with a Retry-After header (in seconds) sized to when the oldest request in the window falls out — wait that long and a slot is guaranteed (barring new traffic).

// 429  +  header: Retry-After: 37
{
  "error": {
    "code": "rate_limited",
    "message": "Sending too fast — per-minute burst limit reached"
  }
}

Per-mailbox cap

Mail sent from a hosted mailbox (webmail / SMTP) additionally carries a fixed per-mailbox hourly cap — a compromised-mailbox guard, plan-independent. Transactional API sends via /v1/emails are governed by the org budgets above, not this cap.

Suppression list

Atrix Mail keeps a suppression list per organization (plus a global list). A recipient lands on it after a hard bounce or a spam complaint. Any send whose to, cc, or bcc includes a suppressed address is refused before it consumes budget:

// 422
{
  "error": {
    "code": "suppressed_recipient",
    "message": "One or more recipients are suppressed",
    "fields": {
      "ava@client.io": "hard_bounce"
    }
  }
}

The fields map names each suppressed recipient and why. Suppression protects your sending reputation: repeatedly mailing addresses that bounce or complain is the fastest way to get filtered to spam. Remove the recipient from your own lists, or manage suppression entries from the dashboard.