OPEN SOURCE EMAIL INFRASTRUCTURE
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.
The world’s fastest-growing email community
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
“With features like traffic shaping, automation and management for IP pools, and all the web hooks that they provide, Kumo allows us to write a lot of automation around it. Kumo is now part of AhaSend where I spend the least amount of time: it's just doing what it's supposed to do without any problems. Nice!”
“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.”
“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.”
“Kumo appears to be capable of far higher single-node throughput than our legacy MTA platform, which has far-reaching implications for increasing our capacity to handle larger campaigns in tighter timeframes. We expect to see significant improvements when warming up new IPs and onboarding new customers also.”
Our Sponsors and Users
Our Community
Lines of Source Code
Pages of Documentation
Discord Members
Stars on GitHub
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.
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."
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
Ongage
Postmastery
EmailConsul
- Tom Mairs
- November 24, 2025
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