Tiers, quotas, and sandbox limits

Every account sends against a daily send cap plus a few per-tier resource limits (mailboxes, custom domains, webhook endpoints, retained storage). New accounts on the trial states (sandbox and pay-as-you-go) also ramp up gradually as they build a clean sending history. This page is the single source for those numbers and for the quota-preflight and rate-limit contracts you read back from the API.

At a glance

The daily send cap above is the tier ceiling. The value actually enforced on any given day is the effective cap, which the trial-state ramp (below) can hold lower until your account is established. Always read your live effective cap from GET /v1/accounts/quota rather than assuming the ceiling.

For sending volume beyond Pro, get in touch with the team.

Daily send cap and the new-sender ramp

• Trial states (sandbox, pay-as-you-go) start at 15 sends/day and lift to 200/day once you have a clean send history. Sandbox's ceiling is 15/day, so a sandbox account stays at 15. Pay-as-you-go's ceiling is also 200/day — each send is still billed individually, but the daily cap is a reputation limit set deliberately below Starter's 233/day, so it stops rising once the ramp reaches it.
• Subscription tiers (Starter, Pro) are coupled to their full ceiling immediately on your first cleared charge, regardless of the ramp. Starter = 233/day, Pro = 1,000/day.

The cap is a rolling per-UTC-day counter. It resets at midnight UTC.

Checking your quota

GET /v1/accounts/quota is an agent-safe preflight: it works with mailbox-scoped agent keys as well as admin keys and returns only send-budget fields (no account-wide detail). Call it before a batch of sends to see how much headroom is left today.

GET /v1/accounts/quota
Authorization: Bearer rly_live_<id>.<secret>

{
  "today": { "count": 12, "limit": 233, "day": "2026-07-02" },
  "sends_remaining": 221,
  "reset_at": "2026-07-03T00:00:00.000Z",
  "scope": "agent",
  "bound_mailbox_ids": ["<mailbox-uuid>"]
}

Warm-up disclosure (present only when active)

When a new-sender warm-up applies to your account, the quota response carries an extra warmup object. Treat it as optional — branch on its presence, and when it is absent your full effective cap applies.

{
  "warmup": {
    "until": "2026-07-05T00:00:00.000Z",
    "shared_domain_daily_limit": 334,
    "velocity_gate_mode": "log_only",
    "reason": "New-sender warm-up protects your sending reputation on the shared pool. Verify your own domain for instant full volume."
  }
}

Verifying your own custom domain moves your sending to an isolated domain, which lifts the shared-pool warm-up.

When you hit the cap

Once today's budget is exhausted, send and reply calls return 429 with the code RATE_LIMITED and a details object you can use to schedule a retry:

HTTP/1.1 429 Too Many Requests

{
  "error": "Daily send limit reached",
  "code": "RATE_LIMITED",
  "details": {
    "daily_limit": 233,
    "sends_remaining": 0,
    "reset_at": "2026-07-03T00:00:00.000Z"
  }
}

sends_remaining is always 0 on this error (that is precisely why it fired), and reset_at tells you when the budget rolls over. Wait until reset_at rather than retrying immediately — a retry before the reset returns the same 429.

A RATE_LIMITED 429 may instead carry details.reason: "new_account_warmup" with a retry_after_seconds value when a new-sender warm-up throttle is in effect. Back off for that many seconds in that case.

RATE_LIMITED is only one of the send-gate outcomes. For everything else that can block a send (suppression, recipient containment, strict-recipient, MX validation, sandbox gates), see the send-gate decision tree; for the full error-code catalog, see the error reference.

Sandbox restrictions

Sandbox is the default trial state on signup. On top of the 15/day cap it adds:

• A temporary trial address. Your sandbox mailbox's address lives on ReplyLayer's shared trial domain and is temporary to the trial — it isn't meant for production use. When you upgrade to a paid tier, you get your own dedicated platform subdomain (or bring your own domain) and choose the production identity your agent sends from going forward. At upgrade the trial mailbox is retired (paused): its threads and messages stay readable and exportable, but it stops sending and stops receiving new inbound — the retirement is immediate, not a grace window.
• A cumulative trial budget of 250 total sends across the whole trial (not per day). When it is exhausted, sends return 403 SANDBOX_TRIAL_BUDGET_EXHAUSTED. Adding pay-as-you-go credits or upgrading to Starter clears it.
• A 30-day trial clock.
• One mailbox.
• A verified-recipient ramp. You can add up to 5 confirmed recipients in your first 72 hours, rising to 25 after that window. Recipients must be confirmed before you can send to them; exceeding the cap returns 403 TIER_LIMIT with a ramp_until timestamp.
• A footer watermark appended to outbound messages. Sending from your own verified custom domain suppresses it.

The simulator exemption

Sends to simulator.replylayer.net addresses (delivered@, bounced@, complained@, suppressed@) — ReplyLayer's own first-party simulator — are exempt from the sandbox verified-recipient confirmation requirement (and are never auto-suppressed), so your onboarding test send in the quickstart works immediately without pre-confirming a recipient. The exact four scenario addresses and their +label forms also bypass the recipient-domain concentration cap below, so one Sandbox account can run all four in the same 24-hour period. Simulator sends still consume daily and cumulative Sandbox allowances, remain in the send-attempt ledger, and are subject to authentication, API rate limits, scanning and review policy, and idempotency. The exemption does not apply to another local part, subdomain, or lookalike domain. The email simulator guide defines each scenario and its billing, suppression, and reputation behavior.

Attachment capabilities by tier

Receiving attachments, their metadata, and viewing previews in the dashboard are available on every tier. The paid gates are:

A bound agent key on a tier without the agent-preview gate receives 403 ATTACHMENT_PREVIEW_DISABLED from the preview route. For the full staging → poll → attachment_ids → consume-once lifecycle and its failure codes, see attachments for agents.

Related

• Quickstart — your first send.
• Send-gate decision tree — why a send was blocked.
• Error reference — the full code catalog.
• Attachments — staging lifecycle and limits.