What is KumoMTA?

KumoMTA is an open source email infrastructure platform designed for enterprises, email service providers, and high-volume senders that need scalable, transparent, and controllable MTA technology. The platform is built for organizations that want to own their email sending infrastructure rather than depend on closed commercial systems. KumoMTA emphasizes performance, with the ability to send tens of millions of messages per hour on a single instance. It is designed to provide the scalability and resilience needed for large-scale email operations without sacrificing visibility or control. Because the platform is open source, teams can inspect the code, understand how the system works, and maintain authority over their deployment. KumoMTA is positioned around long-term stability, cost predictability, fair pricing, operational control, and reduced exposure to vendor lock-in or surprise renewal changes. The platform is supported by a growing community of developers, security researchers, enterprises, and MailOps professionals who contribute to innovation, auditing, vulnerability identification, and ongoing improvement. KumoMTA provides extensive documentation, community resources, a GitHub repository, migration guidance, and support options for teams evaluating or replacing existing MTA infrastructure. Its resources include migration information for platforms such as Hurricane MTA, Momentum, PowerMTA, and SendGrid. The platform is built for teams that need confidence in their email architecture, predictable infrastructure decisions, and the ability to send at massive scale. By combining open source MTA technology, high-volume delivery, code transparency, community stewardship, enterprise support, documentation, and migration resources, KumoMTA helps organizations modernize email infrastructure while keeping control of their operations.

Pricing

Price Starts At:
$0
Price Overview:
KumoMTA is Open-Source and free to use, those interested in support and services can contact us.
Free Version:
Free Version available.
Free Trial Offered?:
Yes

Integrations

Offers API?:
Yes, KumoMTA provides an API
All KumoMTA Integrations
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Screenshots and Video

KumoMTA Queue Architecture

KumoMTA Queue Architecture

KumoMTA Queue Architecture

Company Facts

Company Name:
Kumo Corp
Date Founded:
2023
Company Location:
United States
Company Website:
kumomta.com
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Product Details

Deployment
SaaS
Linux
On-Prem
Training Options
Documentation Hub
Online Training
Webinars
On-Site Training
Support
Standard Support
24 Hour Support
Web-Based Support

Product Details

Target Company Sizes
Individual
1-10
11-50
51-200
201-500
501-1000
1001-5000
5001-10000
10001+
Target Organization Types
Mid Size Business
Small Business
Enterprise
Freelance
Nonprofit
Government
Startup
Supported Languages
English

KumoMTA Categories and Features

Mail Servers

Email Management Software

Data Recovery
Email Archiving
Email Deletion
Email Discovery
Email Monitoring
Email Recall
Queue Manager
Response Management
Routing
Shared Inboxes
Signature Management
Spam Blocker
Whitelisting / Blacklisting

KumoMTA Customer Reviews

Write a Review
  • Reviewer Name: Areeb M.
    Position: Co-founder
    Has used product for: 1-2 Years
    Uses the product: Daily
    Org Size (# of Employees): 1 - 25
    Feature Set
    Layout
    Ease Of Use
    Cost
    Customer Service
    Would you Recommend to Others?
    1 2 3 4 5 6 7 8 9 10

    Flexible, reliable and built for performance!

    Date: Oct 08 2025
    Summary

    A beautiful software for anyone who wants to run production-grade email infrastructure. Stable, fast and modern, and an amazing community.

    Positive

    I love how quick and easy it is to setup KumoMTA.

    It gives you total control over every part of the message delivery which helps you to transform and even fix messages that don’t follow RFC standards.

    The configuration system is easy to use. It's extremely flexible, thanks to its Lua scripting module.

    Well documented, scales beautiful. The webhook (logging) system is also great which makes collecting analytics and statistics really simple.

    I really appreciate the level of personal support that I receive and I am truly grateful for it. In the past, I had a small feature request which was quickly incorporated into the software in under 24 hours.

    Negative

    There's a bit of learning curve at the start, especially for those new to Lua, but this is true for every software/MTA.

    Apart from that, my experience with KumoMTA has been smooth sailing.

    Read More...
  • Reviewer Name: Bjarn B.
    Position: Co-founder
    Has used product for: 6-12 Months
    Uses the product: Daily
    Org Size (# of Employees): 1 - 25
    Feature Set
    Layout
    Ease Of Use
    Cost
    Customer Service
    Would you Recommend to Others?
    1 2 3 4 5 6 7 8 9 10

    Greatest documentation of OSS I ever read

    Date: Oct 10 2025
    Summary

    When I first started using KumoMTA, it took some time to get used to it. However, after all these months I can say I am beyond happy we opted for KumoMTA.

    Positive

    KumoMTA has easily the best documentation that I have ever read. It is super customizable because of the Lua scripting and if you ever get stuck, there's a great community that will help you out.

    Features like webhooks are a blessing and once everything works, it works amazingly well.

    Negative

    It's a lot to take in, knowledge about email is mandatory. Examples in docs could be improved.

    Read More...
  • Reviewer Name: Jesse H.
    Position: Founder
    Has used product for: 2+ Years
    Uses the product: Daily
    Org Size (# of Employees): 1 - 25
    Feature Set
    Layout
    Ease Of Use
    Cost
    Customer Service
    Would you Recommend to Others?
    1 2 3 4 5 6 7 8 9 10

    The only real OSS MTA

    Date: Oct 09 2025
    Summary

    We're rolling this out across our ESP/fleet at the moment. It's been a joy to use and we recommend it to all our friends in the industry.

    Positive

    There's a lot to like with Kumo: easy to spin up instances, easy to scale instances, lightweight, great webhook/event support, and their community is kind so any questions I have get answered quickly in their Discord.

    Negative

    There's no UI/frontend so it's very much for devs. This is fine because we built our own MTA monitoring software.

    Read More...
  • Reviewer Name: A Verified Reviewer
    Position: Technical Director
    Has used product for: 6-12 Months
    Uses the product: Daily
    Org Size (# of Employees): 100 - 499
    Feature Set
    Layout
    Ease Of Use
    Cost
    Customer Service
    Would you Recommend to Others?
    1 2 3 4 5 6 7 8 9 10

    KumoMTA review

    Date: Oct 09 2025
    Summary

    After a period of use, although it was difficult at the beginning, once you become familiar with it, you’ll find that KumoMTA is truly stable and reliable. I hope it keeps getting better.

    Positive

    High performance, extremely stable, and open-source, giving enterprises more options.I replaced Momentum with KumoMTA, which saved me a significant amount of costs. Moreover, Momentum’s support has been getting worse.

    Negative

    Configuration items lack real, effective examples and guidance on how to better implement certain features, methods, and so on.
    Out-of-the-box configurations are limited; this part could actually be developed into a marketplace to enable community participation in co-creation.

    Read More...
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