Substrate is at the core of Microsoft’s mission to empower every organization on the planet to achieve more. The Substrate Transport team builds the global messaging platform that underpins collaboration across Microsoft 365. We own the Exchange Online transport pipeline, processing billions of messages daily—from traditional email to service-to-service communications, enabling secure, reliable delivery across Outlook, SharePoint, Teams, Copilot and emerging M365 experiences.

Substrate Transport is more than an email pipeline - it's a high-scale, intelligent message processing platform that is constantly evolving to meet the ever-increasing demands of new M365 experiences, now including Copilot. Small design decisions can have massive impact on user trust, service health, and feature velocity across M365.

We are modernizing the Transport messaging pipeline to increase reliability, serviceability, and engineering velocity, while embedding AI capabilities directly into Exchange Transport Rules (ETR) to enable smarter, policy‑driven decisions with strong admin control, observability, and correctness guarantees.

As a Senior Software Engineer, you will own critical technical problems end-to-end - from system design and architecture to debugging complex distributed failures in production. You will collaborate closely with partner teams, drive engineering quality, mentor fellow engineers, and contribute to shaping platform direction while staying deeply hands‑on.

We value strong technical ownership, thoughtful design discussions, and learning through real responsibility. The team favors clarity over process, supports continuous improvement, and encourages engineers to grow through challenging problems and visible impact. If you enjoy solving hard distributed systems problems on a global scale, Substrate Transport offers work that truly matters across Microsoft 365.

Microsoft’s mission is to empower every person and every organization on the planet to achieve more. As employees we come together with a growth mindset, innovate to empower others, and collaborate to realize our shared goals. Each day we build on our values of respect, integrity, and accountability to create a culture of inclusion where everyone can thrive at work and beyond.

• Own and drive Transport modernization initiatives from design through production and operations.
• Design and implement resilient, maintainable components in a high‑scale distributed system.
• Embed AI capabilities into ETR in a responsible, engineering‑first manner with clear contracts, guardrails, and diagnostics.
• Raise engineering quality through testing strategies, telemetry, and lifecycle improvements.
• Collaborate across M365 teams, influence stakeholders, and remove technical blockers.
• Mentor through design and code reviews; model high engineering standards.

• Bachelor's Degree in Computer Science or related technical field AND technical engineering experience with coding in languages including, but not limited to, C, C++, C#, Java, JavaScript, or Python OR equivalent experience.
• Strong CS fundamentals and experience building and operating distributed services.
• Proven ability to design, debug, and improve production systemsGrowth mindset, customer focus, and clear technical communication.
• Ability to operate independently and deliver results with limited guidance.

Other Requirements:

• Ability to meet Microsoft, customer and/or government security screening requirements are required for this role. These requirements include but are not limited to the following specialized security screenings: