Mimecast Leadership Team | Mimecast

Ranjan Singh

Chief Executive Officer & Member, Mimecast Board of Directors

Under Ranjan’s leadership, Mimecast is advancing its vision of securing humans, data, and AI together — addressing the convergence of threats that organizations were not built to handle in isolation. As AI reshapes how work gets done and how attacks happen, Ranjan believes the most pressing challenge in cybersecurity is governing all three risk surfaces as one unified problem. Mimecast's platform is built to do exactly that.

Ranjan Singh joined Mimecast as Chief Product & Technology Officer in April 2025, bringing over two decades of experience driving product innovation and delivering exceptional customer-focused solutions. In that role, he led the Product and Engineering organizations, unifying them into a single innovation engine that accelerated Mimecast's platform capabilities and established a rigorous operating culture across both functions.

Before joining Mimecast, Ranjan spent more than three years as a senior leader at Kaseya where he was instrumental in shaping its success, overseeing a global team of 1,100 employees and managing a portfolio of over 40 SaaS products, contributing to $1.5 billion in revenue.

Known for his expertise in integrating products across multiple acquisitions and building multi-product platforms, as well as a customer-centric mindset and meticulous attention to detail, Ranjan's leadership has consistently driven growth, operational excellence, and customer satisfaction.

Prior to Kaseya, Ranjan held key product leadership roles at Crestron Electronics and IPC Systems, where he led technology integration, product development, and strategic execution.

Ranjan earned his undergraduate degree from Victoria University in Melbourne, Australia, and completed his master's degree at New York University. Born in India, and having lived in Australia, and the United States, he is well-versed in navigating international markets and leading teams across cultures. When not driving innovation at Mimecast, Ranjan enjoys spending time with his wife and two children in their hometown in Northern New Jersey.

Rob Juncker

Chief Product & Technology Officer

Rob Juncker is Chief Product & Technology Officer at Mimecast, responsible for driving the product and engineering strategy that powers Mimecast's unified platform for securing humans, data, and AI. Rob brings more than 25 years of security, IT, cloud, and mobile leadership experience, and steps into this role having already played a central part in building the platform he now leads.

In his previous role as Chief Product Officer, Rob led strategy and product management across Mimecast's global product portfolio, working closely with enterprise CISOs and security leaders to shape the company's approach to human and AI risk management.

A trusted advisor to enterprise CISOs and security leaders, Rob regularly chairs executive CISO Advisory Board and Customer Advisory Board sessions with Fortune 500 companies, collaborating on critical security strategies ranging from platform consolidation to AI governance frameworks. His work focuses on helping security leaders transform from reactive threat response to proactive human risk management, addressing the evolving challenges of threats, human behavior, AI, corporate governance, insider risk, configuration complexity, and security stack optimization.

As the former Chief Technology Officer at Code42 (acquired by Mimecast in July 2024), Rob led the development teams that created the Incydr insider risk management solution, transforming the company from an on-premises backup product to a cloud-delivered cybersecurity platform operating at global scale. Prior to Code42, Rob held senior R&D leadership roles at Ivanti and VMware, consistently driving innovation at the intersection of security, cloud architecture, and enterprise IT.

Rob is a frequent keynote speaker at industry events where he shares insights on emerging threat landscapes and practical strategies for security modernization.

Leslie Nielsen

Chief Information Security Officer (CISO)

As Chief Information Security Officer (CISO), Leslie spearheads the company’s global cybersecurity strategy, including threat intelligence, risk management, and detection & response initiatives. Leslie also ensures regulatory compliance, reinforcing Mimecast’s commitment to delivering the highest levels of protection for its more than 42,000 global customers.

With over 25 years of experience in cybersecurity, Leslie is recognized for his ability to drive innovative security strategies and build resilient, high-performing security organizations.

He came to Mimecast from Klaviyo, where he served as Senior Vice President and CISO and played a pivotal role in scaling the company to $1.3 billion in revenue, strengthening its security posture, and leading its security function through their IPO, preparing the organization to meet the rigorous standards of the public markets.

Prior to Klaviyo, Leslie served as SVP and CISO for Nuance Communications. Leslie joined after a devastating malware attack crippled the company, leading their cybersecurity practice through an accelerated transformation that contributed to Nuance Communications becoming one of Microsoft’s largest acquisitions.

Prior to his tenure at Klaviyo, Leslie held senior security leadership positions at several industry-leading organizations. He served as VP and CISO at SAP Concur, and SuccessFactors, as well as CTO at SOS Security. Additionally, Leslie has held senior roles at IBM and ACS (acquired by Xerox), and has served as a member of Google’s CISO Cloud Advisory Board.

Leslie holds a Bachelor of Science in Computer Science from Texas Tech University. He is an avid hiker and a do-it-yourself coffee roaster. He lives in New England with his wife and their canine kid.

Adenike (Nikki) Cosgrove

Chief Marketing Officer

Adenike Cosgrove joined Mimecast in November 2024 as Chief Marketing Officer. Adenike Cosgrove leads Mimecast’s global marketing organization, driving strategic growth and positioning for the company in new and existing markets. Adenike is an accomplished technology executive with expertise across the spectrum of product and business strategy including human risk management, data privacy and compliance. Adenike has close to 20 years’ experience in the cybersecurity industry.

Prior to joining Mimecast, Adenike spent nine years at Proofpoint, serving as marketing leader in EMEA, following the company’s acquisition of Return Path Email Fraud Protection, where she led product marketing and served as Vice Chair of the DMARC.org working group. Earlier in her career, Adenike worked as lead EMEA advisor to security and risk professionals for Forrester Research and Canalys, where she developed a deep understanding of CISO challenges and helped clients with their information and cybersecurity strategies.

Adenike holds a Bachelor of Engineering degree from the University of Hull and a Master of Research, Telecommunications, from University College London. She has lived in Japan, Hong Kong and Nigeria, and currently resides in London.

David Call

Chief Financial Officer

David Call joined Mimecast in May 2023 as Chief Financial Officer. He is an accomplished finance executive with over 20 years of leadership experience in high tech and enterprise software environments. As CFO, Call helps shape the company’s strategic roadmap and plays a key role in helping Mimecast exceed its growth and financial goals, while fostering a collaborative, values-driven culture. Call most recently served as CFO with defi Solutions. Previously, he spent 7 years at McAfee where he served as business unit CFO for both consumer and enterprise security divisions. Call also spent more than 10 years at Intel in various senior leadership finance roles, including their Software & Services Group and the Intel Platform Security Group, before taking a leadership role at McAfee following Intel’s acquisition.

Call has a BS in Accounting from Brigham Young University and an MBA in Finance from UCLA.

Janet Prosper

Chief Human Resources Officer

Janet Prosper was named Chief Human Resources Officer in November 2023. She joined Mimecast in February 2020 as Senior HR Director and has served as interim CHRO since October 2022, and Vice President, Human Resources, since May 2021. Janet leads Mimecast’s inclusion and belonging initiatives and partners with the executive team to shape the company’s people and organization’s strategic roadmap, driven by 'The Mimecast Way’ values.

Janet has nearly three decades of experience leading HR teams in large, global organizations. A considerable part spent working in software/technology organizations undergoing transformation. She also held senior leadership roles with global responsibilities at CareerBuilder, Ciena and Equifax.

During her career she has led all aspects of human resources: transformation, organizational design, change management, culture and employee offering, talent management, and leader development.

Janet has a Bachelor of Arts degree in Business Administration and Human Resources from the University of Westminster.

Chris Wey

Chief Digital Officer

Chris Wey joined Mimecast in 2024. With over 25 years of broad enterprise software experience, Chris leads cross-functional, transformative projects that drive innovation and technology-driven transformation across Mimecast, enhancing the company's ability to compete and succeed in a rapidly evolving market, particularly through the adoption of artificial intelligence.

Most recently, Chris was President of the Data Modernization business unit at Rocket Software, where he led engineering and product management and drove GTM success. Throughout his career, he has held a variety of roles including Corporate Development, Strategic Partnerships, M&A Integration, Engineering, and Sales Operations at Carbonite, Avaya, and IBM. His consistent focus has been on driving growth, organically and inorganically, in rapidly evolving IT markets, and building the robust organizational infrastructure to support that value creation.

Chris holds a Bachelor of Science in Electrical Engineering from Boston University. Born in Switzerland, he and his family take every opportunity to return to Europe for visits.

Graham Douglas

Chief Customer & Revenue Officer

Graham leads Mimecast’s global customer and revenue operations, bringing together customer success, sales, and go-to-market strategy to drive accelerated growth and deepen the company’s unwavering commitment to customer value. With more than 25 years of experience, Graham is a seasoned go-to-market executive known for delivering customer-centric growth and operational excellence as well as building and scaling high-performing teams across the cybersecurity and technology sectors.

Douglas brings more than 25 years of experience building and scaling high-performing teams across the cybersecurity and technology sectors. Prior to Mimecast, he served in senior global leadership roles at Cloudera, Momentive AI, and Oracle, where he managed enterprise sales teams across North America and Europe during a ten-year run. His proven track record of delivering customer-centric growth and operational excellence makes him an ideal fit for Mimecast’s next phase of expansion.

A Scotsman by birth, Douglas graduated from the University of Strathclyde and RMIT University. With his global perspective and extensive experience in cybersecurity and SaaS, he will further strengthen Mimecast’s executive team as the company continues to distinguish itself as a leader in securing human risk. Douglas resides in the US, just outside of Boston, MA.

Chris Dollase

General Counsel

Chris Dollase joined Mimecast in October of 2017 as deputy general counsel, vice president and chief compliance officer. In February 2023, he was promoted to general counsel and senior vice president to lead the legal, compliance and assurance, risk and control teams at Mimecast. Chris and his team work to provide business centric legal advice to all of Mimecast. The team maintains Mimecast’s culture of integrity and compliance while delivering on the company’s growth strategy.

Mimecast's legal team helps 42,000+ customers secure human risk and be successful in an everchanging threat landscape. Chris is an experienced cybersecurity executive who spent 15 years at RSA, The Security Division of EMC, prior to joining Mimecast. He served as lead counsel for RSA and assistant general counsel for EMC and was a member of RSA's leadership team.

Chris has helped navigate Mimecast through seven acquisitions during his tenure, and most recently played a vital role in Permira’s acquisition in May 2022. Chris holds a Doctor of Law J.D. degree from the University of Maryland Francis King Carey School of Law and a Bachelor of Arts in History from Middlebury College.