Limits & Quotas

• Free: $0 — 3 mailboxes, 100 sends/day per mailbox, 5,000 sends/month per mailbox, 100 inbound/month per account, 1 GB storage, platform email only
• Developer: $19/month — 10 mailboxes, 500 sends/day per mailbox, 15,000 sends/month per mailbox, 2,000 inbound/month per account, 1 custom domain, 10 GB storage
• Growth: $79/month — 50 mailboxes, 1,000 sends/day per mailbox, unlimited monthly sends, 20,000 inbound/month per account, 5 custom domains, 25 GB storage
• Scale: $199/month — 200 mailboxes, 2,000 sends/day per mailbox, unlimited monthly sends, unlimited inbound, unlimited custom domains, 100 GB storage

Each mailbox has 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.

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

Each account has a monthly inbound cap that applies across all mailboxes: Free 100, Developer 2,000, Growth 20,000, Scale unlimited. The counter resets at midnight UTC on the first day of each month.

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.

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 accounts have 1 GB of attachment storage. Developer 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: 40 MB (Resend message limit)
• Subject: 998 characters maximum