Limits & Quotas

• Free: $0 — 1 mailbox, 10 sends and 10 receives per month. Exchange mail only between your agent and your verified email address. Upgrade to email anyone. No credit card, no expiry. Allowances reset on the first of each month (UTC). Upgrade for higher limits or a custom domain.
• Solo: $5/month or $60/year — 1 mailbox, 50 sends/day and 500 sends/month per mailbox, 500 receives/month per account, 1 custom domain, 1 GB storage.
• Starter: $19/month or $168/year — 10 mailboxes, 500 sends/day and 15,000 sends/month per mailbox, 2,000 receives/month per account, 1 custom domain, 10 GB storage.
• Growth: $79/month or $708/year — 50 mailboxes, 1,000 sends/day and unlimited sends/month per mailbox, 20,000 receives/month per account, 5 custom domains, 25 GB storage.
• Scale: $199/month or $1788/year — 200 mailboxes, 2,000 sends/day and unlimited sends/month per mailbox, unlimited receives/month per account, unlimited custom domains, 100 GB storage.

Standard mailbox limits use independent daily and monthly send counters. The daily counter resets at midnight UTC, and the monthly counter resets at midnight UTC on the first day of each month. When either limit is reached, send requests return 429 Too Many Requests.

Free allows 10 sends per calendar month, one recipient per message including To, CC and BCC. Exchange mail only between your agent and your verified email address. Upgrade to email anyone. Its monthly cap returns 402 TRIAL_SEND_LIMIT with resetsAt; the legacy error-code name does not mean the Free plan expires.

The current send counts are available on the mailbox object (dailySendCount, monthlySendCount) and via GET /v1/account (sentToday, sentThisMonth aggregates).

Paid accounts have a monthly inbound cap that applies across all mailboxes: Solo 500, Starter 2,000, Growth 20,000, Scale unlimited. The counter resets at midnight UTC on the first day of each month.

On paid plans, inbound messages received after the cap is reached are still ingested and stored, but gated: webhook/SSE payloads arrive as stubs (with over_limit: true and no body or attachments) and single-read GET endpoints return 402 INBOUND_LIMIT_EXCEEDED. List endpoints filter over-limit messages and report the hidden count in metadata.overLimitCount. Upgrading the plan or the first-of-month reset unlocks every gated message in place — a subsequent call returns them with full content.

Free allows 10 receives per calendar month. Exchange mail only between your agent and your verified email address. Upgrade to email anyone. Mail outside these rules or above the receive allowance is discarded, with no backlog on renewal or upgrade.

Current usage is exposed via quota headers on every API response (X-Robotomail-Inbound-Quota, X-Robotomail-Inbound-Warning) and on GET /v1/account. See 402 INBOUND_LIMIT_EXCEEDED.

Free and Solo accounts have 1 GB of attachment storage. Starter accounts get 10 GB, Growth accounts get 25 GB, and Scale accounts get 100 GB. Storage usage is tracked per-account and visible via GET /v1/account (storageUsedBytes and storageLimitBytes). Uploading an attachment that would exceed the limit returns 413 Payload Too Large.

• Signup: 5 requests per hour per IP (check X-RateLimit-Remaining header)
• Send: Subject to daily and monthly send limits per mailbox plus Resend rate limits

There is no general API-wide rate limiter beyond these specific limits. The daily and monthly send caps plus Resend throttling are the primary constraints for normal usage.

• Per attachment: 25 MB maximum file size
• Total message: 25 MB across all attachments
• Subject: 998 characters maximum