Success Is About Focus and Making Choices: Interview with Marc van Zadelhoff, CEO of Mimecast

I recently went one-on-one with Marc van Zadelhoff, CEO of Mimecast.

Adam: Thanks again for taking the time to share your advice. First things first, readers would love to learn more about you. How did you get here? What experiences, failures, setbacks, or challenges have been most instrumental to your growth? 

Marc: Thanks for having me! I’m proud to serve as the CEO of Mimecast, leading a team that secures more than 42,000 customers worldwide. It’s been a long journey to this point, and I’ve been able to take things from each of my past roles that have helped me become a better leader. 

The most defining experience that shaped my leadership journey was when IBM acquired a startup called Consul in 2007, where I was SVP Marketing and Strategy. Adapting from a small company to a Fortune 500 enterprise was a challenge – and the culture shock impacted not just me, but my entire team. However, this ended up being a rewarding challenge that empowered me to learn and grow fast. 

During my time at IBM, I was one of the founders of IBM Security, a new business unit that I led as GM and CEO, and spearheaded over a dozen acquisitions. Developing and leading IBM Security was a great honor and I’m proud to say that it was a very strong business. When I departed for my next opportunity, the business had grown to 8,000 global employees and $2.5bn in annual revenue. 

Prior to IBM and Consul, I spent time as a consultant and a venture capitalist. I learned a lot in each position, and that knowledge helped shape my future leadership roles. One of the most important learnings was the ability to make decisions with limited or incomplete data. In senior roles, you rarely have the luxury of time, but you always must do what’s best for the business. 

I saw firsthand how success and failure followed patterns, and I learned that sound strategy trumps most else. That lesson proved invaluable at IBM, and now Mimecast, where I often must make quick decisions with less data. 

Adam: In your experience, what are the key steps to growing and scaling your business?

Marc: Strategy is everything. 

I’m a firm believer that strategy and making the right chess moves is key. People often say execution eats strategy for lunch, and maybe that’s true in some cases, but I’d argue that when the stakes are high, great execution can only take you so far without a solid strategy as the foundation.

A related, critical factor is staying close to customers. The answers to your business’s problems aren’t within the building – you need to get out and talk to your customers. When I was at IBM, I spent more time talking to CISOs than anyone else. That deep understanding helped me bridge the gap between product and customer needs, ensuring we were always moving in the right direction.

Adam: What is your best advice on building, leading, and managing teams? 

Marc: It’s a cliché, but you’re only as good as your team; and saying that is the easy part, putting it into action is what counts. First, set lofty goals and measure progress against them. Be there to support your team, offer guidance, and help them grow. But also, know when it’s time to make tough decisions and switch out players if necessary to keep pushing the team forward. Leadership is about finding the right balance of support and tough calls when required.

Adam: What are the most important trends in technology that leaders should be aware of? What should they understand about them?

Marc: The focus in the cybersecurity sector must shift from infrastructure to humans. Organizations have spent a lot of time and money securing their IT infrastructure but paid little attention to securing the employees behind the keyboards. Ignoring this in the modern threat landscape is not a recipe for success. 

Workplace collaboration tools like Slack, Zoom, and Microsoft Teams are used daily and have become essential for productivity, but they've also significantly expanded the digital attack surface. Simply throwing point solutions at the problem will not work, there are too many tools to monitor and consider. 

To keep pace and stay secure, organizations must evolve to a human-centric cybersecurity approach that effectively connects the dots between humans and technology. By deploying a connected platform, instead of a disparate set of tools, organizations can protect themselves from collaboration attacks, insider threats, and employee mistakes. 

We also can’t talk about technology trends without mentioning the rise and transformation of AI. Our State of Email and Collaboration Security Report found that 80% of organizations are concerned about new threats posed by AI. A staggering figure that clearly shows a big shift has already taken place.

GenAI, specifically, has really changed the cybersecurity landscape, on both sides of the battlefield. According to The World Economic Forum's Global Cybersecurity Outlook 2025, 42% of organizations experienced a successful social engineering attack in the past year, a clear sign of increased malicious adoption of AI. Organizations must combat by layering AI technologies with proven defense methods to keep ahead. 

One thing I’m not hearing enough in the conversation around AI is the importance of responsible and ethical use of the technology. For AI to fulfill its potential, organizations must leverage it both ethically and transparently. Mimecast is proud to lead the charge here, we recently became the first cybersecurity company to achieve AI Management Systems standard ISO 42001. 

Adam: What do you believe are the defining qualities of an effective leader? 

Marc: A leader won’t go far without curiosity, commitment, and humility. In my consultancy days, I learned early on that these three traits are essential, and they've stuck with me ever since. In leadership, there’s often an expectation to be a "know-it-all." If you can maintain curiosity, though, it keeps you accessible and constantly questioning success or wondering if you’re where you need to be.

Commitment is about doing the hard work – being with your team, meeting with difficult client,s and getting in the trenches. It’s not just about delegating.

And humility? It’s simple: don’t be arrogant or condescending. A leader who is humble is someone people can trust and respect.

Adam: How can leaders and aspiring leaders take their leadership skills to the next level?

Marc: First, when you start a new role, you need to realize that your prior greatness does not convey. Each new team needs to earn your trust, and vice versa. So, I spend the first few weeks listening and learning and not trying to prove I’m the smartest or have all the answers. Many answers that seem logical in week one prove to be foolish by week 10.

Next, do focus the team by defining a clear strategy and narrowing priorities. At Mimecast, when I arrived, it felt like we were trying to do too many things. We narrowed it around a tighter strategy and then executed quickly.

Nurture and develop the team next. If you’re lucky, you have room to add 1-2 new people that can bring new perspective and energy to the table. And then it’s team curation: each individual must be excellent, but even more they must work well as a team. Patrick Lencioni’s book on ‘Five Dysfunctions’ is a great guide here.

Finally, no one likes a micro-manager, but I’ve pushed myself to be closer to the details than is my nature. Being hands-off and a delegator doesn’t really work in tech. You need to be a micro leader: empower your teams but probe and execute down to the details.

Finally, seek and take feedback. Push your team to criticize you and get a coach who will!

Adam: What are your three best tips applicable to entrepreneurs, executives and civic leaders? 

Marc: As a CEO of a cybersecurity company who lives and breathes security, my #1 tip is to protect your business, assets, customers and employees through tech infrastructure, as well as understanding and mitigating human risk. Far too often, we see companies failing compliance checks or employees falling victim to scams as simple as clicking a malicious link in their email inbox. While deploying tools to mitigate that risk is crucial, remember that employees are the first line of defense against cyberattacks. Effectively protecting your employees is essential to secure the full business. 

Throughout my career, I’ve had to pivot and adapt across industries, from venture capital to marketing and cybersecurity. For any entrepreneur or leader, the ability to quickly learn and adjust to new environments is paramount for long-term success. Innovation is constantly evolving, and flexibility allows you to thrive in the face of challenges.

Finally, building a strong team is fundamental. The strongest companies aren’t built on one individual’s skills but on the collective expertise and leadership of their people. Recruiting top talent is important but so is investing in and developing leaders within your organization to ensure sustained growth and innovation.

Adam: What are your best tips on the topics of sales, marketing and branding? 

Marc: It all comes down to one key idea: know your customer and know your product. Any sales, marketing or branding actions that are devoid of this knowledge are useless. Knowing the customer is crucial because they’re the ones casting a vote for your product. There’s also a trap of overusing buzzwords that can dilute your message. Keep it simple and meaningful.

To truly learn about your customers, you have to engage directly. Sales calls are a great starting point, but understanding how to demo the product is equally important. Many marketing people shy away from demos, thinking they aren’t technical enough. The reality is, if you can use everyday apps from the app store, there’s no reason you can’t get up to speed on how your company’s product works. The more hands-on you are, the better you'll be at crafting the right message and connecting with your audience.

Adam: What is the single best piece of advice you have ever received? 

Marc: The best advice I’ve ever received is that success is about focus and making choices. You can excel at two things at a time – whether that’s your job, family, or social life – but trying to be great at all three at the same time is unrealistic. As a CEO, you have to acknowledge that something will inevitably take a backseat, and that’s okay. It’s about prioritizing what’s most important and being intentional with your time and energy. For me, that’s being a CEO and husband/father. The rest can wait!

Adam: Is there anything else you would like to share?

Marc: Big, audacious goals are key – both individually for leaders and for organizations. 

The day-to-day grind can be tough. Having a north star sets a clear vision that will help keep leaders and their teams focused and motivated, even when the work becomes tough. 


Adam Mendler is an entrepreneur, writer, speaker, educator, and nationally recognized authority on leadership. Adam is the creator and host of the business and leadership podcast Thirty Minute Mentors, where he goes one-on-one with America's most successful people - Fortune 500 CEOs, founders of household name companies, Hall of Fame and Olympic gold medal-winning athletes, political and military leaders - for intimate half-hour conversations each week. A top leadership speaker, Adam draws upon his insights building and leading businesses and interviewing hundreds of America's top leaders as a top keynote speaker to businesses, universities, and non-profit organizations. Adam has written extensively on leadership and related topics, having authored over 70 articles published in major media outlets including Forbes, Inc. and HuffPost, and has conducted more than 500 one on one interviews with America’s top leaders through his collective media projects. Adam teaches graduate-level courses on leadership at UCLA and is an advisor to numerous companies and leaders. A Los Angeles native, Adam is a lifelong Angels fan and an avid backgammon player.

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