How we helped Mailgun by Sinch reduce cost per signup by 10%—all through cold outbound

The challenge

Mailgun by Sinch, trusted by giants like Microsoft, American Express, and Lyft, had a powerful product and plenty of awareness. But paid channels were getting expensive, and their team wanted to add a more predictable and scalable outbound engine that could reduce acquisition costs and create a second source of high-quality signups.

They turned to Leadamax to make cold outbound a true growth channel.

Our approach

✅ Persona + List Optimization
We worked with Mailgun’s growth team to identify the highest converting personas (developers, product teams, tech startups, SaaS platforms). We used Scrapeamax + Clay + Apollo to enrich and qualify the right lists globally.

✅ Device-Like Targeting with Data
We brought our version of device-level optimization into cold email: segmenting messaging based on company size, job title, and tech stack to personalize at scale and increase response rates.

✅ Cold Email Copy Testing
We created and A/B tested highly specific cold email sequences focused on Mailgun’s strongest value prop: deliverability, reliability, and email scale. Just like ad copy testing, but for inboxes.

✅ Reply Management + Conversion Flow
Our reply handling process filtered out noise and prioritized leads most likely to sign up and convert. We built follow-up sequences specifically to move prospects from reply → booked demo → signed up for Mailgun.

✅ All via cold outbound
No ad spend. No bidding wars. Pure cold email execution from start to finish.

The results

✔️ 10% decrease in cost per signup vs. paid channels
✔️ Consistent pipeline of highly qualified leads
✔️ New scalable outbound channel to complement paid and organic efforts
✔️ High reply rates and better conversion-to-signup ratio than previous cold outreach attempts

With Leadamax, Mailgun added a second predictable engine of growth—and freed up ad spend to scale even further.