Mimecast Appoints Leslie Nielsen as Chief Information Security Officer

LEXINGTON, Mass., Aug. 27, 2025 (GLOBE NEWSWIRE) -- Mimecast, a global cybersecurity leader redefining how organizations secure human risk through precision-engineered AI, today announced that Leslie Nielsen has joined the company as Chief Information Security Officer (CISO).

Nielsen is a 25+ year cybersecurity veteran who joins Mimecast from Klaviyo, a high-growth marketing automation platform, where he served as SVP and CISO. At Klaviyo, he played a critical role in scaling the company to $1.3B in revenue, fortifying its defenses and leading its security function through IPO readiness, positioning the organization to meet the rigorous demands of the public markets.

“We sought out a leader who can see beyond the noise and hype to deliver an innovative security platform, and Leslie fit the bill perfectly,” said Mimecast CEO Marc van Zadelhoff. “I’m excited to welcome him to the Mimecast team and for the expertise he brings in scaling world-class security at a time where cyber defense is at its most critical. Leslie’s proven experience leading security teams will be invaluable to safeguarding our customers and hardening our resilience strategy.”

As CISO, Nielsen will spearhead Mimecast’s global cybersecurity strategy, driving the company’s threat intelligence, risk assessment, incident response initiatives, as well as ensuring regulatory compliance, reinforcing Mimecast’s commitment to providing the highest levels of protection for its more than 42,000 global customers.

“I’m thrilled to join Mimecast on their mission to secure the human layer in the new age of AI-powered security threats,” said Nielsen. “The industry is at a pivotal point where defense strategies must place humans at the center, and Mimecast has long been at the forefront of human side of security. I look forward to building on the company’s strong foundation and helping shape its next chapter of innovation and resilience.”

Prior to Klaviyo, Nielsen held SVP and CISO roles at Nuance Communications, SAP Concur and SuccessFactors and the CTO role at SOS Security, along with senior roles at IBM and ACS (acquired by Xerox). He also was a member of Google’s CISO Cloud Advisory Board. He earned his Bachelor of Science in Computer Science from Texas Tech University.

About Mimecast
Mimecast is a global cybersecurity leader redefining how organizations secure human risk through precision-engineered AI. Its AI-powered, API-enabled connected human risk platform is purpose-built to protect organizations from the spectrum of cyber threats. Integrating cutting-edge technology with human-centric pathways, our platform enhances visibility and provides strategic insight.

By enabling decisive action and empowering businesses to protect their collaborative environments, our technology safeguards critical data and actively engages employees in reducing risk and enhancing productivity. More than 42,000 businesses worldwide trust Mimecast to help them keep ahead of the ever-evolving threat landscape.

From insider risk to external threats, customers get more with Mimecast. More visibility. More agility. More control. More security.

Mimecast and the Mimecast logo are either registered trademarks or trademarks of Mimecast Services Limited in the United States and/or other countries. All other third-party trademarks and logos contained in this press release are the property of their respective owners.

Press Contacts
Tim Hamilton
Principal, Global Corporate Communications Manager
+1 603-918-6757
thamilton@mimecast.com

General inquires
press@mimecast.com

A photo accompanying this announcement is available at https://www.globenewswire.com/NewsRoom/AttachmentNg/2b5f6680-96cd-48a2-8728-d6af2ecc5c8c

Leslie Nielsen

Mimecast CISO

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