Senior Software Engineer II, Messaging Platform

About the Messaging Platform Group

HubSpot’s Messaging Platform Group develops the core infrastructure that supports communication across all HubSpot products. Every message—whether from a marketing campaign, a personalized sales email, a service alert, or an automated workflow—goes through the systems our team creates.

Our systems handle enormous scale: we send over 8 billion emails, SMS, and WhatsApp messages each month, record billions of events, and enable customers to link their personal inboxes directly to the HubSpot CRM. For us, reliability, security, and deliverability are non-negotiable—they're essential for maintaining customer trust and ensuring business success.

We continuously push the limits of large-scale messaging by developing intelligent routing, improving our custom mail transfer agent (MTA), expanding our IP network, and optimizing overall deliverability to ensure every message reaches its destination.

About the Email Sending Infrastructure Team

The Email Sending Infrastructure team manages the core backend systems that ensure reliable email sending and receiving across HubSpot. They develop and operate HubSpot’s in-house mail transfer agent (MTA) and oversee a globally distributed network of email sending IPs supporting billions of messages monthly. In addition to just sending emails, they design smart routing systems that control message flow through our infrastructure, guaranteeing safe, efficient, and large-scale delivery.

To maintain this ecosystem, the team creates tools and services that constantly monitor network performance, reputation, and deliverability. They emphasize observability, resilience, and control, giving HubSpot and its customers confidence that messages arrive on time and where needed. Their work, combining distributed systems, networking, and performance engineering, forms the foundation of how customers communicate and grow with HubSpot.

What You’ll Do

As a Senior Backend Engineer on the Email Sending Infrastructure team, you will:

• Design, build, and maintain high-scale backend services that support email sending, routing, and deliverability across the HubSpot platform.
• Contribute to the development of HubSpot’s in-house MTA and systems managing global IP networks.
• Enhance reliability, observability, and performance within a mission-critical messaging pipeline.
• Collaborate closely with infrastructure teams, product managers, and deliverability experts to ensure safe, consistent, high-quality message delivery.
• Lead design discussions, participate in architectural decisions, and help shape long-term technical strategy.
• Write clean, testable, and maintainable code that follows best practices for distributed systems and network-intensive workloads.
• Engage in code reviews, mentor fellow engineers, and foster a culture of learning and operational excellence.

We’re Looking For Someone Who:

• Has 7+ years of backend engineering experience working on highly available, scalable systems.
• Is comfortable working with technologies like Java, Kotlin, MySQL, Kafka, HBase, and Kubernetes (experience with specific stacks is less important than strong fundamentals).
• Understands distributed systems, networked services, and high-throughput data flows.
• Enjoys solving complex reliability, throughput, and performance challenges.
• Communicates clearly and collaborates effectively with engineers, PMs, designers, and domain experts.
• Builds with empathy for the end user—and for the downstream teams who build on our infrastructure.
• Thrives in an environment where curiosity, pragmatism, and resourcefulness drive impact.

Why This Role Matters

Email is one of the most critical and widely used communication channels at HubSpot, and the infrastructure supporting it directly impacts how our customers do business. The systems you build and maintain in this role will power the sending of billions of messages each month, enabling companies of all sizes to reach their audiences, nurture relationships, and drive revenue. Your work will influence deliverability, latency, reliability, and trust—factors that determine whether our customers’ messages land in inboxes or disappear into the void.

By strengthening HubSpot’s email infrastructure, you help safeguard our global sending reputation and enable us to grow safely as our customer base and message volume expand. The features you develop will lay a foundation not only for email but also for future messaging channels and intelligent routing options across the platform. Ultimately, this role influences how effective, reliable, and powerful HubSpot’s messaging experience is for millions of users worldwide.