Organizations using Office 365 and G Suite turn to GreatHorn to protect against today’s greatest cybersecurity threats: targeted phishing attacks, business email compromise, malware and ransomware.


Cloud email calls for cloud-native email security. 

Office 365 and G Suite require a modern, cloud native email security solution to protect against advanced threats, which legacy email gateway technology just isn’t designed to catch. Only GreatHorn delivers a next generation email security platform purpose-built for cloud-based communications systems.

Built on a foundation of machine learning and automation, GreatHorn delivers the industry’s most effective and comprehensive email security solution, and can be deployed and operational in less than 5 minutes. With its proprietary dataset built from hundreds of millions of uniquely analyzed threats, GreatHorn combines the intelligence, fidelity and precision necessary to prevent attacks from becoming breaches.


We provide comprehensive protection against email-based threats.

Email continues to be the #1 attack vector and your employees will click phishing links, no matter the amount of security training.

Only GreatHorn is effective at protecting against targeted phishing, socially engineered attacks, malware and ransomware at the endpoint so they don’t progress into organizational attacks.

We disrupt cyber attacks — not your email performance.

GreatHorn delivers email security without requiring changes to MX records or mail flow. That means no performance delays, delivery risk or downtime.

Improve your security without impacting your end user’s email experience or productivity.

We integrate easily into your cloud email environment and deploy in under 5 minutes.

GreatHorn is cloud native and integrates seamlessly with Office 365 and G Suite without the need for agents or plugins. The solution provides universal protection across mail clients and devices – desktop and mobile.

GreatHorn is easy to set up and provides ultra-fast time to value. Out-of-the-box policies provide immediate protection from day one.

We save you a lot of time.

GreatHorn’s automated and configurable response actions reduce the time and effort spent by IT and security teams identifying and responding to suspicious emails by more than 80 percent.

GreatHorn helps you rapidly meet your email security requirements without adding complexity.

We provide post-delivery threat remediation and response.

Not every malicious email has readily apparent indicators of compromise. Some contain links or attachments that are altered only after they reach a user’s inbox.

Only GreatHorn is able to take action on emails — indefinitely — after they have arrived in your end users’ mailboxes.

We’re building a powerful community with shared intelligence.

When you choose GreatHorn, you become part of a growing community of organizations that benefit from shared threat intelligence.

With real-time intelligence and analysis from our community of cloud email users and other sources, GreatHorn will alert your organization to emergent threats before they reach your environment.


Incredible organizations from startups to Fortune 500 companies trust GreatHorn.


Founded and led by a team of security industry veterans with decades of experience solving complex cybersecurity challenges.


Kevin O’Brien, CEO & Founder

Kevin O’Brien is GreatHorn’s CEO and Co-Founder. Under Kevin’s leadership, GreatHorn has become the world’s leading next generation email security company, analyzing billions of messages and stopping phishing attacks targeting a global customer base of organizations, both public and private. He brings deep industry experience, having been an early member of multiple successfully exited security companies, including CloudLock (Cisco), Conjur (CyberArk), and @stake (Symantec).

Prior to founding GreatHorn, Kevin was Vice President of Marketing at Conjur, where he built the early go-to-market team responsible for initial market positioning and growth. Previously he led product marketing and sales engineering efforts at CloudLock, the leading cloud access security company that now has more than 6 million enterprise users.

In addition to his role at GreatHorn, Kevin serves as co-chair for the Mass Technology Leadership Council’s cybersecurity group, and is a frequent speaker at key cloud cybersecurity and industry events. He has presented at the RSA Security Conference, Xconomy’s What’s Hot in Cybersecurity Conference, Microsoft’s Innovation Outreach Program, the MassTLC Cybersecurity Conference, and has been featured in TechCrunch, NPR Marketplace, Mashable, Forbes, CSO Magazine, and more.

Kevin holds a bachelor’s degree from the University of Massachusetts Amherst, and holds a black belt in Aikido.


Raymond Wallace III, CTO & Co-Founder

Ray Wallace is GreatHorn’s Chief Technology Officer and Co-Founder. Ray is responsible for GreatHorn’s overall product strategy, development and continuous innovation for its next generation email security platform.

Ray brings more than a decade of experience building complex security and software systems and product platforms. He has deep domain experience in application and database security, front and back-end infrastructure and domain analytics.

Prior to GreatHorn, Ray held senior engineering roles at companies including Brainshark, Courion and Application Security.

Ray studied computer science at Rochester Institute of Technology.


Ann Sharon, Vice President of Operations

Ann Sharon is Vice President of Operations at GreatHorn. Ann is responsible for all operational aspects of GreatHorn’s processes and procedures to drive consistency and optimization including GreatHorn’s go to market and compliance programs.

Ann is a seasoned technology operations executive, experienced in operations and program management, proficient in leading cross functional programs and initiatives in early-stage start-ups, high growth, and mature companies.

Prior to joining GreatHorn, Ann served as Vice President of Business Operations for CloudLock (acquired by Cisco), where she helped drive the go to market strategy and lead many cross functional programs. Prior to CloudLock, Ann managed the EMC secure remote support portfolio overseeing both the product management and program management aspects. Ann began her career in the IDF serving in the elite Air Force computer unit.

Ann holds a high-tech MBA from Northeastern University and a BSc in Industrial Engineering from TheTechnion Institute of Technology.


Catherine Arizan, Director, Product

Catherine Arizan is GreatHorn’s Director of Product. Catherine leads the company’s core product design and development processes, as well as product marketing, where her significant industry experience and background in security marketing has contributed to the successful launch of multiple products and positioning of GreatHorn as the industry’s leading next generation email security solution.

Prior to joining GreatHorn, Catherine was Director of Content Marketing at IANS, where she was responsible for identifying security needs across multiple member organizations. She has also held early stage roles at Animatron and Validly.

She is a frequent speaker and presenter, and has addressed both technical and business audiences on design, product, and security topics. Catherine holds two bachelor’s degrees from Hunter College, one in media studies and one in comparative literature.


Wesley Davis, Team Lead, Customer Success

Wesley Davis is Team Lead for the GreatHorn Customer Success organization. Wes leads a team responsible for helping new and existing customers optimize their use of the GreatHorm platform, through onboarding and operationalization, product documentation and technical support.

Wes was an early member of the GreatHorn team and joined the company as a Business Development Representative supporting sales campaigns and operations. Prior to that, he worked in Business Development at Conjur, a DevOps security company (acquired by CyberArk).

Wes began his career teaching English as a Second Language at various schools in Boston after participating in the Fulbright teaching program in Austria. He holds a bachelor’s degree from Hamilton College with a double major in German language and medieval history.


Caitlin McLaughlin, Controller

Caitlin McLaughlin is the Controller at GreatHorn. Caitlin is responsible for all aspects of financial accounting and reporting at GreatHorn. She brings more than 10 years of technical financial accounting and reporting experience which she has acquired in both privately-held and publicly traded company settings.

Prior to joining GreatHorn, Caitlin was a Senior Manager in Accounting & Financial Reporting at Aegerion Pharmaceuticals. At Aegerion, she managed the entire external financial reporting process including the preparation of all required external financial materials for all public filings, coordinated and oversaw all Sarbanes-Oxley related activities over the financial reporting processes, and was able to provide technical accounting on relevant financial accounting areas such as: revenue recognition, share-based compensation, purchase accounting, and debt restructuring.

Prior to joining Aegerion, Caitlin began her career as an auditor at RSM (formerly known as, Vitale, Caturano & Company), where she provided both technical and operational financial knowledge to both privately held and publicly-traded companies across various industries including: software and technology, financial services and life sciences.

Caitlin holds a bachelor’s degree in accountancy from Bentley University and maintains an active license as a Certified Public Accountant in the Commonwealth of Massachusetts.


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GreatHorn Names Ann Sharon Vice President of Operations

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