Senior Solution Architect - Email & Collaboration Security

Senior Solutions Architect – Email & Collaboration Security – London UK

Why This Role Exists

The Email & Collaboration Security (ECS) product line sits at the intersection of some of the most consequential challenges in enterprise security today: AI-augmented threats, sprawling collaboration surfaces, multi-cloud delivery complexity, and the expectation that detection and response capabilities keep pace with a threat landscape that does not wait.

This architecture is not greenfield. It carries two decades of accumulated product decisions, integration contracts, and operational constraints. The right candidate understands why that history matters before proposing how to move beyond it. Reasoning about legacy shape and evolutionary trajectory simultaneously is not optional; it is the job.

The successful candidate will serve as connective tissue across product management, engineering, and the broader Architecture Leadership Team — turning customer and business problems into coherent, deliverable technical direction, and owning the decisions that give ECS engineering teams a stable foundation to move fast with quality.

AI-First Ways of Working

Mimecast is an AI-first engineering organisation. This is not a cultural aspiration — it is an operating expectation. The person in this role is expected to use AI tools as a genuine, daily part of how they work: for design exploration and iteration, documentation, analysis, prototyping, and research synthesis.

This means having a real, practised opinion on where AI tooling accelerates quality decisions and where it introduces risk. It also means designing systems that incorporate AI components thoughtfully: understanding the implications of LLM integration, agent boundaries, prompt and data-contract stability, and evaluation coverage for AI-driven features.

Candidates who treat AI tooling as optional or experimental are not the right fit for this role. The expectation is fluency and daily practice, not passing familiarity.

The ECS Domain

ECS covers the following product and capability areas:

Email threat detection and prevention

Email security efficacy

Collaboration security

DMARC analyzer

Data platform and observability

Analysis and Response

End user application integration

Internal operations enablement

What You Will Do

Lead from Problem Space, Not Solution Space

The role engages at the problem-framing stage, not after requirements have already hardened into tickets. This means facilitating workshops with PMs, UX, and engineers to surface real customer constraints and articulate what good looks like in business and user terms before any technical shape is proposed.

Own Integration Contracts as Product Artefacts

The durable interfaces — APIs, event contracts, data schemas — that connect ECS capabilities to the broader Mimecast platform are first-class artefacts owned by this role. They outlast individual features, and the coordination work that makes integrations actually land across teams and time is part of the remit.

Build the Architectural Context Engineering Teams Operate Inside

ADRs, service interaction patterns, NFR targets, and data contracts are not documentation — they are the substrate that lets engineering teams and AI-assisted development workflows make consistent decisions at scale. The artefacts produced in this role are clear, reasoned, and durable.

Govern Without Blocking

Governance is a mechanism for alignment and acceleration, not gatekeeping. Structure and discipline are introduced where they reduce risk or improve quality — and removed where ceremony adds cost without value. The role engages the Chief Architect early, pushes back constructively when platform standards do not fit the ECS context, and helps teams close decisions with conviction rather than endless review.

Reason About Cost and Unit Economics

Infrastructure choices are sized, cost trajectories modelled for new architecture work, and unexpected spend is flagged with a proposed remediation. The frame is cost per outcome — per protected mailbox, per remediated incident — not just monthly AWS spend.

Communicate at Every Altitude

A one-page decision record that lands with engineers, a solution brief that holds up under senior architecture review, a strategy narrative that resonates with product and commercial leadership — this role operates across all of those registers. Whiteboard sessions produce actual decisions, not just richer ambiguity.

What You Will Bring

Breadth Over Depth — and Knowing the Difference

10+ years building and operating production SaaS systems, with at least 3 years in a Senior Architect or equivalent role carrying product-shaping responsibility

A genuinely broad architectural lens — thinking about system shape, data flows, and organisational constraints rather than reaching for the nearest deep technical rabbit hole

Comfort operating across cloud-native patterns (AWS, Kafka, managed services, distributed event architectures) at high throughput — able to reason about trade-offs with confidence, without needing to be the most technically specialist person in the room

Product Understanding — Not Just Technical Understanding

Prior close collaboration with Product Managers and UX designers, with an understanding of jobs-to-be-done framing and a real opinion on what makes a product bet good — not just a technical bet

Genuine customer orientation: asking what problem the customer has before asking how to build the feature

Understanding of SaaS unit economics, the commercial implications of architectural choices, and how to reason about scale from a product perspective as well as a systems one

The Right Mindset for Complex, Inherited Systems

An understanding of what twenty years of software history means in a production system — no assumption of greenfield, and no treatment of legacy as only debt; it is accumulated context

Structure and discipline as cognitive defaults, not imposed processes — thorough, well-reasoned artefacts, and a habit of leaving things clearer than they were found

An ability to connect dots across a large picture with many moving parts, make a call, and communicate it clearly — rather than waiting for certainty that will not arrive

Self-Direction and Strategic Initiative

A proactive self-starter who identifies the right problems to work on without being told, and drives them to resolution

Comfortable acting independently within a set of principles, while keeping the right stakeholders informed and in sync — not seeking permission, but maintaining alignment

Thrives with ambiguity and treats it as a problem to be structured, not a reason to pause

Learning Orientation — Not Encyclopaedic Knowledge

Able to reach a solution even without all the knowledge in front of them — a problem-solver who knows how to navigate to an answer, not a mnemonic database

AI tooling treated as a core capability multiplier, with a real daily practice in design work, documentation, research synthesis, and prototyping

Stays ahead of where the market and the technology are going, and brings that signal back into product and architecture decisions

Bonus Points

Background in email security, threat detection, DLP, identity, or data platforms

Familiarity with agentic AI, MCP (Model Context Protocol), or LLM application architecture

Experience with eval design for AI features, product discovery practices, or data contract / data mesh approaches

Exposure to M365 or GWS integration patterns, SMTP relay architecture, or cloud-native security SaaS

What We Offer

Impact : architecture decisions that protect millions of mailboxes and shape the technical direction of one of Mimecast's core product pillars

Voice : a direct working relationship with the Chief Architect and a genuine say in technology direction — not an advisory lane

Senior peers : a small, high-trust Architecture Leadership Team where everyone opera