Case Study · 2017
Employee #11 to 200+: Scaling Email Security for the Bank of England
Joined Tessian as Employee #11—the first client-side engineer—and helped scale from 15 people to 200+ employees. Deployed to the Bank of England and Dentons. Later acquired by Proofpoint.
Client
Tessian
Date
2017-07
Service
Full-Stack Development, Enterprise Deployment, Email Security, CI/CD
Key Results
- → Joined as Employee #11 (1st Client-Side Engineer) at a 15-person startup.
- → Helped scale to 200+ employees (Sequoia, Accel, Balderton backed).
- → Deployed to Bank of England & Dentons using on-premise Ansible scripts.
- → Later acquired by Proofpoint for their AI-powered email security platform.
The Challenge
Tessian (originally CheckRecipient) was building AI-powered email security—software that could detect and prevent misdirected emails, data exfiltration, and phishing attacks.
The problem: their customers were banks and law firms. These weren’t companies that would install a Chrome extension and call it a day. They needed on-premise deployments, strict security compliance, and enterprise-grade reliability.
When I joined as Employee #11, Tessian had about 15 people. They needed an engineer who could build client-side software that would satisfy the security requirements of the world’s most paranoid organizations.
What I Did
Building the Outlook Add-in
The flagship product was an Outlook add-in that would warn users before they sent emails to the wrong recipient:
- Built and maintained the Outlook Add-in that integrated with Microsoft’s email client
- Led the migration from legacy VB.NET to modern C#—cleaning up years of technical debt
- Created developer tooling and build pipelines to speed up the team’s workflow
Enterprise Email Infrastructure
Beyond the client-side work, I got pulled into the backend infrastructure:
- Co-engineered a high-throughput email gateway (MTA) that processed millions of emails per day
- The MTA had to handle enterprise email volumes with sub-second latency
- Built the Concourse CI/CD pipeline for the email infrastructure
Bank of England & Dentons Deployments
The biggest validation: deploying to institutions where email security wasn’t optional:
- Deployed to Bank of England and Dentons (one of the world’s largest law firms)
- These were on-premise deployments—no cloud, no shortcuts
- Wrote and maintained Ansible scripts for reproducible, auditable deployments
- Worked directly with client security teams to satisfy their compliance requirements
Scaling the Company
Over two years, I watched and contributed to Tessian’s growth:
- Helped scale from 15 to 200+ employees
- Participated in hiring, onboarding, and establishing engineering practices
- Saw the company raise from Sequoia, Accel, and Balderton—the top VCs in the space
The Tech Stack
- C# / .NET (Outlook Add-in)
- Legacy VB.NET (migrated away)
- High-throughput MTA (email gateway)
- Concourse CI/CD
- Ansible (on-premise deployments)
- Enterprise security compliance
The Results
- Employee #11 → 200+ — Scaled with the company through hypergrowth
- Bank of England — Deployed to one of the world’s most security-conscious institutions
- Dentons — Trusted by a top-10 global law firm
- Acquired by Proofpoint — Exit validation for the platform we built
Tessian became a leader in AI-powered email security. The Outlook add-in I helped build and the email gateway I co-engineered processed millions of emails per day for enterprise customers.
The ultimate validation came after I left: Proofpoint acquired Tessian, integrating the technology into their enterprise security platform. The systems we built are now protecting some of the world’s largest organizations.
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