How Omnisend scaled to 2.5 billion emails a month with Sinch Mailgun

Omnisend was built on the premise that ecommerce marketing should be simple. Since launching in 2014, the platform has grown together to serve more than 150,000 ecommerce brands worldwide.

Desislava Zhivkova, Head of Deliverability and Compliance Operations, says that reliable sending infrastructure, seamless onboarding, and revenue-boosting tools are essential to their customers’ success. In the company’s early years, though, the infrastructure underneath couldn’t keep up with the growth above it.

Omnisend was scaling fast, and their previous provider created friction at customer onboarding. Every time a new user added a sending domain, the provider automatically sent a highly technical confirmation email directly to that customer. Most of them had no idea Omnisend used a third party for this step, so they ignored it. 

Onboarding stalled, but the problem was largely invisible until someone reached out to support (when reputational damage was already done).

Omnisend needed an infrastructure partner with the API flexibility to reshape how domain verification worked entirely on their terms. That’s what drew them to Sinch Mailgun.

“Mailgun gave us the API flexibility to eliminate those onboarding bottlenecks – specifically, we were able to remove the unnecessary domain verification email flow entirely. That was a real unlock for us.”

Desislava Zhivkova Head of Deliverability and Compliance Operations at Omnisend

Beyond the onboarding fix, the move to Mailgun gave the deliverability team full control over dedicated IP pool management. This is crucial at the scale Omnisend operates, where maintaining consistent sending quality across a global customer base requires precise, proactive oversight.

Migrating sending infrastructure at Omnisend’s volume wasn’t a simple lift. IP warm-up, volume sequencing, and close coordination with Mailgun’s team were all part of making the transition work.

“The integration required careful planning – migrating sending infrastructure at scale always carries risk, and ensuring IP warm-up and volume management were handled correctly was a priority,” Desislava said. “Mailgun really supported us throughout this process, and once we were through the transition, the API proved stable and reliable for our needs.”

Today, Omnisend sends more than 2.5 billion emails a month on behalf of its customers and maintains a 99% delivery rate. The infrastructure runs quietly in the background – which is exactly the point.

“Mailgun handles the infrastructure layer that our platform depends on for email delivery. As a company that takes deliverability seriously, having a sending infrastructure that operates reliably at scale is what matters most to us.”

Desislava Zhivkova Head of Deliverability and Compliance Operations at Omnisend

As Omnisend continues to expand its omnichannel capabilities, email remains foundational. And as its customer base keeps growing, so does the standard that reliable infrastructure has to meet.