Cloud email cybersecurity startup GreatHorn Inc. today said it has raised $13 million in new funding to expand its existing services in email security.

The Series A-1 round was co-led by RRE Ventures and .406 Ventures and included Techstars Ventures, V1.VC and Uncork Capital. Including the new funding, GreatHorn has raised $21.8 million to date.

Founded in 2015, Boston-based GreatHorn offers a service that safeguards cloud email from advanced threats such as individual and brand impersonations, credential theft attempts, malware, ransomware and advanced social engineering-based phishing attacks. It does so by protecting organizations before, during and after an email attack through a proactive threat detection engine, in-the-moment user education and incident response capabilities.

The company’s product connects directly to Office 365 and G Suite without any need for DNS editing or other modification to existing email setups.

The company claims to be in its third year of triple-digit revenue growth, including a rapid expansion into the enterprise market. While not providing a list of customers, one of them is MuleSoft LLC.

“Despite decades of experience and billions of dollars spent, the email security industry is no closer to making email safe for businesses,” Raju Rishi, a general partner at RRE Ventures, said in a statement. “By rethinking how we approach email security, GreatHorn has delivered a platform that comprehensively protects enterprises against the rising sophistication of today’s threats.”

The cloud-based email security market is a niche, but a report from Modor Intelligence says it will have a compound annual growth rate of 8.7% through 2024.

Image: GreatHorn