# Ekx Resend > Transactional email with Resend — sending from a route handler or cron, React Email templates, domain verification and DNS, dry-run mode for local development, and delivery webhooks. Use when sending an alert, receipt, magic link or digest email, when email is not arriving, or when setting up a new sending domain. - Skill: `ekinoxis-evm/ekx-resend` (Agent Skill) - Install (CLI): `npx skillmds@latest add ekinoxis-evm/ekx-resend` - Raw SKILL.md: https://api.skillmd.com/api/skills/ekinoxis-evm/ekx-resend/raw - Safety review: pending - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Web & Frontend - Author: Ekinoxis-evm (https://skillmd.com/u/ekinoxis-evm) - Updated: 2026-09-22 - Page: https://skillmd.com/skills/ekinoxis-evm/ekx-resend --- # Resend Our transactional email vendor across the portfolio. There is a bundled `resend` skill in this Claude installation and a **`resend` MCP server** — both are authoritative over this file for API detail. Docs: https://resend.com/docs --- ## Environment ```bash RESEND_API_KEY= # SECRET RESEND_FROM= # "Ekinoxis " RESEND_FROM_EMAIL= # same thing, older name — pick one per repo RESEND_DRY_RUN=true # local: log instead of send ``` `RESEND_DRY_RUN` came out of a scheduled scanner and is worth copying everywhere. That scanner emails on every detected opportunity; without a dry-run flag, a local debugging session sends a few hundred real emails and burns the domain's reputation. ```ts if (process.env.RESEND_DRY_RUN === "true") { console.log("[resend:dry-run]", { to, subject }); return { id: "dry-run" }; } ``` --- ## Sending ```ts import { Resend } from "resend"; const resend = new Resend(process.env.RESEND_API_KEY!); const { data, error } = await resend.emails.send({ from: process.env.RESEND_FROM!, to: [user.email], subject: "Oportunidad detectada — spread 4.2%", react: , // or: html / text headers: { "X-Entity-Ref-ID": opportunity.id }, // idempotency hint }); if (error) { // Resend returns { data: null, error } — it does NOT throw. console.error("resend failed", error); } ``` **Resend returns errors, it does not throw.** Code that only wraps the call in `try/catch` will report success on every failure. Always destructure and check `error`. Batch (up to 100 per call): ```ts await resend.batch.send([{ from, to, subject, html }, /* … */]); ``` --- ## Domain setup Verify the sending domain in the dashboard, then add the DNS records it gives you: **SPF**, **DKIM**, and a **DMARC** record. All three. Sending from an unverified domain works only to your own address; sending from a verified domain without DMARC lands in spam at Gmail and Outlook. Use a subdomain for transactional mail (`mail.ekinoxis.xyz`) so a reputation problem never touches the root domain's deliverability. --- ## Templates React Email components live alongside the app and are type-checked with the data they render — better than HTML strings: ```tsx export function OpportunityEmail({ opportunity }: { opportunity: Opportunity }) { return ( Spread {opportunity.spread}% {opportunity.marketA} vs {opportunity.marketB} ); } ``` Always provide a plain-text fallback — some clients, and most spam filters, want one. --- ## From a cron A scheduled scan that emails on a hit. Two rules: 1. **Deduplicate before sending.** Store what was already alerted in Supabase and check before send, or a stuck condition emails on every tick. 2. **Rate-limit.** Resend's default is 2 requests/second. A loop over 200 recipients needs `batch.send` or a delay, not 200 concurrent calls. --- ## Gotchas 1. **Errors are returned, not thrown.** Check `error`. 2. **Unverified domain** silently limits delivery to your own address. 3. **Missing DMARC** → spam folder at the big providers. 4. **2 req/s default rate limit.** 5. **No dry-run flag** in local dev = real emails from your laptop. 6. **`to` is an array.** A bare string works in some SDK versions and not others; always pass an array.