What I learned writing cold emails based on real issues on each prospect's website

I run a small web design agency, and for years our cold outreach looked like everyone else's. Reply rates were close to zero. 😅

So we tried something different: before writing to a company, we checked their website and opened the email with one specific, real issue we found.

Here's what one of those first emails looked like:

Subject: Your contact form isn't sending

Hi Laura,

I was on your website this morning and noticed the contact
form returns an error when you submit it, so you might be
missing enquiries without knowing it.

Happy to tell you exactly what's happening (no strings attached).

José Manuel

🧠 What we learned

1. One concrete issue beats a list of five.
People reply to an email that sounds like a human noticed something, not like an automated audit.

2. Lead with the problem, not your service.
The pitch can wait until the second email.

3. Follow-ups matter… until they reply.
Nothing kills trust faster than an automated "just bumping this" after they've already answered.

4. Small businesses are grateful.

Some reply just to say thanks for pointing out a broken form, and that's a conversation started.

We ended up turning this workflow into a tool: Boneleads, which launched today 👉 https://www.producthunt.com/products/boneleads

But I'm genuinely curious about the approach itself:

What's the most effective opening line you've ever used (or received) in a cold email? 👇