Klaviyo is an ecommerce-focused CRM and email/SMS marketing platform, especially strong with Shopify. It has a REST API, webhooks, and a built-in CDP. Marketing only (not transactional).
Pair Klaviyo (marketing) with MailKite (transactional + inbound) for Shopify stores.
A minimal, copy-paste starter. Swap in your own domain and API key.
import { verifyWebhook } from "@mailkite/client";
// MailKite POSTs every inbound email at your domain as JSON.
// Point a route at this handler in the MailKite dashboard.
export default async function handler(req: Request) {
const raw = await req.text();
const sig = req.headers.get("x-mailkite-signature") ?? "";
// Reject anything not signed by your webhook secret
const ok = await verifyWebhook(sig, raw, process.env.MK_WEBHOOK_SECRET!);
if (!ok) return new Response("bad signature", { status: 401 });
const email = JSON.parse(raw);
// Route into Klaviyo: open a ticket, create a task, store a record
await routeIntoName(email); // email.from · email.subject · email.text
return new Response(JSON.stringify({ ok: true }));
}Point a domain, set one SMTP endpoint, send your first email in minutes. Unlimited domains, no credit card.