OPEN SOURCE EMAIL INFRASTRUCTURE

for enterprises and high-volume senders

Fast

KumoMTA is architected for the performance needed by enterprise senders, whether it's sending several million messages per hour through a single server, or scaling horizontally using Docker and Kubernetes.

Flexible

KumoMTA can replace straightforward configurations or be deeply integrated into your MailOps environment thanks to our Lua scripting engine and support for technologies including webhooks, AMQP, Kafka, Vault, Prometheus, Grafana, and direct database access.

Open-Source

KumoMTA is released under the Apache 2 OSI-approved license, with the ultimate transparency of having our sourcecode hosted on Github. Our community is actively involved and contributing to make KumoMTA better every day.

Architecture

Revolutionized

A leap ahead of re-architected commercial offerings

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Performance

Redefined

Send 10’s of millions of messages an hour on a single instance

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Confidence

Restored

No more black boxes when you own the code

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The world’s fastest-growing email community

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Invest in your business,
not someone else’s business model

The control and continuity you need without the risk, volatility, or pricing shocks that come with commercial providers

check_circle_Long-term stability
Long-term stability
The confidence that your investment will remain secure and supported
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Cost predictability and fairness
No surprise price hikes or exploitative renewals
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Control and resilience
Guaranteed access to the technology and authority over your deployment
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A trusted partnership
A relationship built on stewardship and transparency
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Performance, scalability, and control
No surprise price hikes or exploitative renewals
The Fastest Growing Email Community

Our Sponsors and Users

Our Community

90000

Lines of Source Code

650 +

Pages of Documentation

700 +

Discord Members

350 +

Stars on GitHub

Kumo is proud to partner with the industry's leading integrators, services, and deliverability providers

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THE KUMO COMMUNITY
by the numbers

Making KumoMTA better every day

Expedited innovation and vulnerability identification is performed by a global community of independent developers, security researchers, and enterprises who are continually auditing code and identifying improvements.

Join the Kumo Discord Community today chevron_right
90,000
Lines of code
650+
Pages of documentation
800+
Discord members
350+
Stars on GitHub
Latest news and info

Our Memberships

BenDyer

Taguchi Marketing

Ben Dyer

"We’ve known Kumo’s founders and worked with them for many years, That personal connection was critical.

The fact they’re involved was enough to get us over the line to becoming a customer."

TomK

CEO

Tom Kuzler

"I really enjoy our MTA being open source and being able to see the issue and commit pipelines. It gives us a lot of transparency around where issues might sit that we never had before with a closed source MTA and lets us transparently know when bugs that are important to us are resolved. The pace of iteration and change that ultimately helps our end users is vastly improved."

Our Partners

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Integration Partner

Ongage

Ongage is an email marketing platform that helps your business to personalize engagements and drive conversions through data.
postmastery
Services Partner

Postmastery

Postmastery is a leader in email deliverability and email infrastructure management. They are an authorized EU-based support provider of Kumo for the purpose of selling and providing Support Services to KumoMTA End Users.
EmailConsul
Deliverability Partner

EmailConsul

EmailConsul is a comprehensive email analytics and monitoring solution designed to enhance email deliverability. The platform provides DMARC analytics, inbox placement, threat intelligence, blocklist monitoring, in-depth reporting, and more to help businesses maintain a healthy sender reputation and ensure messages reach their intended audience.

The Winter 2025 Release

The Fall release of KumoMTA was only six weeks ago and was one of the largest, with more than 20 enhancements. That...

Digging MIME

One of the common requests we get is about examining the message by parts to perform security checks, redact private...

What we did on our summer vacation. JK - this is a big one

You have waited much longer than normal for a new KumoMTA release, but the wait is over. We spent the summer grinding...
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Choose the Best MTA

Find out more about how you can break free of the commercial license trap while leveraging the best MTA for enterprise senders.

Let's Talk

Chat with our founders and learn how easy it can be to move to KumoMTA.