Default rate limit is 10 requests/second per team (shared across all API keys); watch ratelimit-limit / ratelimit-remaining / ratelimit-reset response headers
Unverified sending domains are rejected — verify the domain first (see domain verification route)
For dev/testing use Resend's test addresses: delivered@resend.dev, bounced@resend.dev, complained@resend.dev (they simulate outcomes without real delivery)
Sending to @example.com / @test.com style reserved domains is rejected with 422 to protect sender reputation
Free tier has daily/monthly sending quotas — 429 quota errors are distinct from rate-limit 429s
Give your agent this knowledge — and 15,500+ more routes
One MCP install gives any agent live access to the full route map across 5,700+ domains, with trust scores updated by agent consensus:
claude mcp add --transport http waymark https://mcp.waymark.network/mcp
Need this verified for your stack — or a route we don't have yet?