Email Automation for Startups

Your app is live. Users are signing up. Now you need to send them emails:

You could use Mailchimp (please don't). Or you could pick a modern email platform built for developers. Let's compare three favorites: Loops, Customer.io, and Resend.

Loops: The Newsletter First Platform

Best for: Startups who want simple, beautiful newsletters with transactional emails on the side

What it does well:

What it doesn't do:

Pricing:

Perfect for: Early-stage SaaS sending weekly newsletters + transactional emails.

Customer.io: The Marketing Automation Beast

Best for: Growth-stage startups ready for sophisticated user journeys

What it does well:

What it doesn't do:

Pricing:

Perfect for: Companies with product-market fit ready to optimize conversion funnels.

Resend: The Developer's Email API

Best for: Developers who want complete control over their email infrastructure

What it does well:

What it doesn't do:

Pricing:

Perfect for: Technical teams who want to own their email infrastructure.

The Real Comparison

| Feature | Loops | Customer.io | Resend | |---------|-------|-------------|--------| | Transactional emails | ✅ Simple | ✅ Advanced | ✅✅ Best | | Marketing campaigns | ✅ Good | ✅✅ Excellent | ❌ DIY | | Visual workflow builder | ⚠️ Basic | ✅✅ Advanced | ❌ None | | React Email support | ✅ Yes | ❌ No | ✅✅ Native | | Free tier generosity | ✅✅ Great | ⚠️ Limited | ✅ Good | | Learning curve | ✅ Easy | ⚠️ Steep | ⚠️ Technical | | Price at scale | ✅ Affordable | ❌ Expensive | ✅✅ Cheap |

Our Recommendation by Stage

Pre-seed / MVP (< $10K MRR)

Choose Loops if you need newsletters + basic transactional emails.

Choose Resend if you're technical and just need transactional emails.

Seed Stage ($10-100K MRR)

Stick with Loops if your email needs are simple.

Switch to Customer.io if you need complex automation (onboarding sequences, win-back campaigns, etc.).

Series A+ ($100K+ MRR)

Customer.io for sophisticated marketing automation.

Resend for transactional emails at scale (move marketing to Customer.io).

Real-World Setup

Loops (Next.js)

import { LoopsClient } from "loops"

const loops = new LoopsClient(process.env.LOOPS_API_KEY)

// Send transactional email
await loops.sendTransactionalEmail({
  transactionalId: "welcome_email",
  email: user.email,
  dataVariables: {
    name: user.name,
    loginUrl: "https://app.yoursite.com"
  }
})

Resend (Next.js + React Email)

import { Resend } from "resend"
import { WelcomeEmail } from "@/emails/welcome"

const resend = new Resend(process.env.RESEND_API_KEY)

await resend.emails.send({
  from: "Team <team@yoursite.com>",
  to: user.email,
  subject: "Welcome to the team!",
  react: <WelcomeEmail name={user.name} />
})

Customer.io

import { APIClient } from "customerio-node"

const client = new APIClient(process.env.CUSTOMERIO_API_KEY)

// Track event to trigger campaign
await client.track(user.id, {
  name: "signed_up",
  data: { plan: "free" }
})

The Bottom Line

Start with Loops. Graduate to Customer.io when you need complex workflows. Use Resend if you're technical and want full control.

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Next Week: We're taking a break from tools to look back at 2024. What changed? Which tools won? What trends should you ignore? Our year-in-review issue.

Stay sharp, The Startup Starter Kit Team

P.S. We're using Loops to send this newsletter. No surprise - it's perfect for what we need. What email platform are you using? Hit reply and tell us your story.