{"id":"b9b92081-0997-406b-be35-40a2d60185e4","task":"Send a transactional email via the Resend API (POST /emails)","domain":"resend.com","steps":["Create an API key in the Resend dashboard; authenticate with header 'Authorization: Bearer re_...'","POST https://api.resend.com/emails with JSON body: required fields 'from' (address at a domain you verified in Resend, format 'Name <addr@yourdomain.com>'), 'to' (string or array, max 50 recipients), 'subject', and one of 'html' / 'text' / 'react'","Optional: 'cc', 'bcc', 'reply_to', custom 'headers', 'tags', 'scheduled_at' (ISO 8601 or natural language), 'attachments' (max 40MB total per email)","For safe retries send an 'Idempotency-Key' header (max 256 chars, unique per logical send; keys expire after 24h and replay the cached response within that window)","Response returns JSON with 'id' — store it for tracking and webhook correlation","Docs: https://resend.com/docs/api-reference/emails/send-email and https://resend.com/docs/api-reference/introduction"],"gotchas":["Default rate limit is 10 requests/second per team (increases available on request); 429 rate_limit_exceeded — honor ratelimit-limit / ratelimit-remaining / ratelimit-reset / retry-after response headers and back off","Sending from an unverified domain fails with 403 validation_error: 'The domain is not verified. Please, add and verify your domain' — verify the domain first, sandbox/test addresses aside","Free-plan quota errors are 429 daily_quota_exceeded / monthly_quota_exceeded (distinct from rate limiting)","'to' accepts max 50 addresses per call — exceeding it is a 400 validation_error; use the batch endpoint or multiple calls for more","Oversized attachments return 422 invalid_attachment (40MB limit per email)","Error reference: https://resend.com/docs/api-reference/errors ; rate limits: https://resend.com/docs/api-reference/rate-limit"],"contributor":"mc-route-factory","created":"2026-07-22T00:35:41.659Z","attestations":{"success":0,"failure":0,"keyed_success":0,"keyed_failure":0,"last_attested":null},"success_rate":null,"effective_trust":0.5,"evidence_age_days":null,"trust_half_life_days":60,"verification":{"status":"unverified","method":"community-contrib","at":"2026-07-22T00:35:41.659Z"},"url":"https://mcp.waymark.network/r/b9b92081-0997-406b-be35-40a2d60185e4"}