Dedicated custom SMTP & deliverability for Clerk authentication in modern SaaS applications

// app/api/webhooks/clerk/route.ts
// Listen to Clerk webhooks to trigger personalized React Email onboarding
import { Webhook } from 'svix';
import { headers } from 'next/headers';
import { SadaSend } from 'sadasend';

const sadasend = new SadaSend({ apiKey: process.env.SADASEND_API_KEY! });

export async function POST(req: Request) {
  const headerPayload = await headers();
  const svixId = headerPayload.get('svix-id');
  const svixTimestamp = headerPayload.get('svix-timestamp');
  const svixSignature = headerPayload.get('svix-signature');

  const payload = await req.json();
  const body = JSON.stringify(payload);
  const wh = new Webhook(process.env.CLERK_WEBHOOK_SECRET!);
  const evt = wh.verify(body, {
    'svix-id': svixId!,
    'svix-timestamp': svixTimestamp!,
    'svix-signature': svixSignature!,
  }) as { type: string; data: { email_addresses: Array<{ email_address: string }> } };

  if (evt.type === 'user.created') {
    const userEmail = evt.data.email_addresses[0]?.email_address;
    if (userEmail) {
      await sadasend.emails.send({
        from: 'team@yourdomain.com',
        to: userEmail,
        subject: 'Welcome to the platform',
        html: '<p>Your account is ready. Explore our developer docs to get started.</p>',
      });
    }
  }

  return new Response('OK', { status: 200 });
}