I Built a SaaS in One Day — Here's Everything I Learned

Peter Park — Thu, 22 Oct 2026 01:16:02 +0000

What I Built

ColdMailAI — an AI-powered cold email generator that creates hyper-personalized outreach emails in seconds.

The Tech Stack

Frontend: Next.js (App Router)
AI: OpenAI API (GPT-4)
Hosting: Vercel (free tier)
Payments: PayPal integration
Total cost to build: $0

Why I Built It

I was tired of spending 30 minutes writing each cold email for B2B outreach. Most templates felt generic, and personalization took forever. So I built a tool that:

Takes a company name, prospect role, and your offer
Generates a personalized cold email with AI
Matches the tone to the prospect (formal, casual, direct)

Lessons Learned

1. Ship fast, improve later

My MVP had literally one feature: generate a cold email. No login, no dashboard, no analytics. Just input → output. That was enough to validate the idea.

2. Free tier is essential for B2B tools

Nobody signs up for a paid tool they've never tried. The free tier lets people experience the value before committing.

3. $9/month is the sweet spot for new SaaS

After researching pricing for similar tools, $9/month felt right. Low enough to be a no-brainer, high enough to be sustainable.

4. Distribution > Product

Building the product took one day. Getting people to find it? That's the real challenge. SEO, social media, and community engagement are where the real work begins.

5. Reddit will ban your self-promotion

Learned this the hard way. Value-first content in communities like r/sales and r/Entrepreneur works much better than direct promotion.

What's Next

Adding follow-up email sequences
LinkedIn DM generation
Email analytics and A/B testing

Try It

If you're in B2B sales or outreach, give it a try: getcoldmail.com — it's free, no signup needed.

Would love feedback from the DEV community!

DEV Community: Peter Park