Senior Principal Engineer - Email Security

Senior Principal Engineer – Email Security (Mimecast)

Join us in tackling email processing challenges at an immense scale with our innovative Email Security team! Mimecast’s Email Security product processes billions of emails from millions of users on thousands of servers each day.

As Senior Principal Engineer, you will lead the development of our next‑generation, cloud‑based Email Security product for the Message Transfer Agent and mail transport protocols. You will be the subject‑matter expert for all aspects of Mail Transport and Protocols (SMTP, MIME, DKIM, SPF, DMARC, ARC, etc.), and you will handle the entire development lifecycle—from design, development, and testing to deployment, maintenance, and improvement.

You will also drive technical excellence and innovation within the team while mentoring junior engineers.

• Own and lead all aspects of Mail Flow and Message Transfer protocols.
• Set long‑term technical strategy.
• Account for all aspects of deployments and operationalisation in the Dev Sec Ops  model.
• Identify, communicate and establish plans to mitigate risks.
• Design new features or enhancements based on high‑level architectures and product requirements.
• Work on a global, highly distributed infrastructure.
• Engage with the team through collaboration, problem‑solving, and teamwork.
• Continually improve team efficiency, personal skills, and team skills.
• Take ownership and create accountability within the team.
• Lead security reviews of designs and implementations.
• Act as a technical lead within the team, fostering collaboration and teamwork.
• Apply technology trends and industry innovations to our products.
• Coach and mentor team members in areas of expertise.

• 15+ years of software development experience.
• Expertise building and maintaining Message Transfer Agents and email transport systems.
• Deep knowledge of all the transport and security protocols (SMTP, MIME, SPF, DKIM, TLS, ARC, etc.).
• Strong object‑oriented programming skills following SOLID principles.
• Accomplished in core Java, and experienced in building REST/HTTP microservices.
• Familiarity with Jenkins CI/CD pipelines and Terraform.
• Experience with containerization technologies such as Docker and Kubernetes.
• Proficient in AWS services.
• Proven ability to build high‑volume, scalable, distributed back‑end services.
• Expertise in multi‑threaded software engineering, designing, implementing, and troubleshooting concurrent systems to optimise performance and resource utilisation.
• Proficient in leveraging AI tools, such as Cursor, to enhance software engineering practices.
• Excellent collaboration, influencing, negotiation, coaching, mentoring, and coalition‑building skills.
• Strong verbal and written communication skills.
• A great team player with demonstrable experience delivering superior software products via Agile methodologies.
• Continuous learning mindset, keeping abreast of related industry technologies, tools, and standards.

Join our Email Security team to accelerate your career while working with cutting‑edge technologies and contributing to impactful projects for our customers. You will be immersed in a dynamic environment that recognises and celebrates your achievements.

Mimecast offers formal and on‑the‑job learning opportunities, a comprehensive benefits package that helps our employees and their families sustain a healthy lifestyle, and opportunities to work in cross‑functional teams to broaden your knowledge.

• Fosters a culture of collaboration, communication, performance, and learning.
• Drives innovation and creativity within and between teams.
• Introduces employees to priorities outside of their immediate realm.
• Ensures important interpersonal relationships and connections with one another and our community.

The base salary range for this position is £120,000 to £180,000 plus benefits. The range represents the minimum and maximum new‑hire compensation for this role. The position may also be eligible for incentive plans and additional benefits, in accordance with company policy and local regulations. Final offers reflect these considerations and may vary accordingly.