# We migrated our email infrastructure to KumoMTA. Here's why it matters for you.

DevFeed: [We migrated our email infrastructure to KumoMTA. Here's why it matters for you.](<https://devfeed.tech/articles/we-migrated-our-email-infrastructure-to-kumomta-here-s-why-it-matters-for-you-16087.md>)

Original publisher: [Read original article](<https://postmarkapp.com/blog/we-migrated-our-email-infrastructure-to-kumomta-heres-why-it-matters-for-you>)

Author: Alex Burch (aburch@activecampaign.com)

Published: 2026-03-31T17:56:00Z

Content type: article

Language: en

Sources: [Postmark (en-US)](<https://devfeed.tech/sources/postmark-en-us.md>)

Topics: [migration](<https://devfeed.tech/topics/migration.md>), [cloud-infrastructure](<https://devfeed.tech/topics/cloud-infrastructure.md>), [Open Source](<https://devfeed.tech/topics/open-source.md>), [Rust](<https://devfeed.tech/topics/rust.md>), [API](<https://devfeed.tech/topics/api.md>)

Tags: [api](<https://devfeed.tech/tags/api.md>), [engineering](<https://devfeed.tech/tags/engineering.md>), [hardware](<https://devfeed.tech/tags/hardware.md>), [infrastructure](<https://devfeed.tech/tags/infrastructure.md>), [migration](<https://devfeed.tech/tags/migration.md>), [open-source](<https://devfeed.tech/tags/open-source.md>), [real-time](<https://devfeed.tech/tags/real-time.md>), [rust](<https://devfeed.tech/tags/rust.md>), [traffic-management](<https://devfeed.tech/tags/traffic-management.md>)

## AI overview

Postmark migrated its email infrastructure from PowerMTA to KumoMTA, an open-source, Rust-based mail transfer agent. The company says the change improves its ability to manage traffic in real time, scale on cloud infrastructure, and customize email delivery operations.

## Source excerpt

If you've been sending email through Postmark lately, your messages have been moving through an entirely new engine (and you probably didn't notice a thing). That's exactly how we wanted it. We've completed our migration from PowerMTA to KumoMTA, an open-source, high-performance mail transfer agent (MTA). Every email Postmark sends now runs through KumoMTA. It's the biggest infrastructure change we've made in years, and it sets the stage for everything we want to build next. Wait, what's an MTA? An MTA,or mail transfer agent,is the software responsible for delivering your email. When you send a message through Postmark's API, our application processes it, and the MTA takes it from there: queuing, connecting to the recipient's mail server, and handling the SMTP transaction that gets your message where it needs to go. Think of it as the delivery truck for your email. You hand us the package, and the MTA figures out the fastest route to the door. Why we made the switch Postmark has been running PowerMTA for years, and it served us well. But as our needs evolved, the limitations became harder to work around. The biggest issue? Traffic management. Our previous setup made it difficult for our deliverability and operations teams to respond in real time when something went sideways, like when a mailbox provider temporarily blocks an IP address. In those moments, you need to be able to back off traffic, reroute, and adjust shaping on the fly. Our old configuration didn't give us that flexibility at the MTA level, which meant we were sometimes limited in how quickly we could resolve delivery issues. Beyond that, our previous infrastructure was running on aging hardware that was increasingly difficult to maintain. Scaling required a lot of manual effort, and customizing behavior to match Postmark's specific needs was constrained by the proprietary nature of the platform. We needed something that could grow with us, and that we could shape to fit the way Postmark works, not the