KumoMTA review (2026): is the free plan enough?
Open-source mail server for high-volume, self-run email sending
Black Friday: is there a KumoMTA sale?
KumoMTA report card
Fair · out of 4.0 · graded Nov 13, 2026
Best for a free high-volume mail server you run yourself
KumoMTA is an open-source mail transfer agent for high-volume senders running their own infrastructure, configured in Lua. The software is free, but you run it yourself, and paid support starts at $5,000 per billion messages a year.
Who KumoMTA is for
- Fits if you're an engineering team running your own high-volume sending
- Works for senders moving off a commercial mail server who can write Lua
Who KumoMTA is not for
- Skip it if you want a point-and-click setup, since configuration is done in Lua
- Tight if you need support: Silver is business hours only, and Enterprise has no published price
- Not for you if you want a hosted service, as you run it yourself
- Watch out: the pages don't say which operating systems are supported
Why KumoMTA gets a 2.2
Five grades, each with its reason. The GPA is their average: an A is 4 points, an F is none.
- CValue for moneyThe software is free under Apache 2, but you host it yourself, and paid support starts at $5,000 per billion messages a year.
- BFree plan and trialEvery feature is free to run, with community help on Discord. You do need your own server to use any of it.
- BFeaturesHigh-volume sending, Lua policy scripting, traffic shaping and IP pools, with hooks into Kafka, AMQP, Prometheus, Grafana and Vault. Nothing in the listing shows a gap in the job.
- DEase of useNo store rating on record. It's configured in Lua scripting on your own servers, so it suits engineers.
- CPlatforms and integrationsSoftware for your own servers, listed for Linux, with Docker and Kubernetes. No dashboard or hosted version.
What these grades rest on. Graded from this listing, whose facts were read from KumoMTA's own pages on 13 November 2026. Not based on using the product, and shorter than our full reviews. How we review and grade.
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<a href="https://toolgpa.com/tools/kumomta#review"><img src="https://toolgpa.com/badge/kumomta.svg" alt="KumoMTA: 2.2 GPA on ToolGPA" width="196" height="56"></a>Where KumoMTA stands among email sending services
KumoMTA's GPA of 2.2 is higher than 14 of the 50 other email sending services we grade, and level with 10.
It stands best on free plan and trial (B, above 35 of 50) and worst on ease of use (D, above 0).
Its paid plans start at $416.67 a month when paid by the year, against a middle price of $15 for the category: 40 of the 41 others that charge start lower.
On features, ease of use and platforms it scores 2.0 out of 4. 30 tools score higher and cost less.
Each grade against the category
Every bar is all 51 email sending services we grade, cut by the letter each got. KumoMTA’s own letter is outlined.
- CValue for moneyAbove 8 of 50, level with 16
- BFree plan and trialAbove 35 of 50, level with 13
- BFeaturesAbove 30 of 50, level with 20
- DEase of useAbove 0 of 50, level with 6
- CPlatforms and integrationsAbove 0 of 50, level with 16
Price against what you get
Each dot is one of 44 email sending services. Further left costs less, and higher up scores better on features, ease of use and platforms. Point at a dot to see which tool it is.
Features, ease of use and platforms, averaged
What paid plans start at, a month (each step along is roughly double) →
- The best score at each price
- Has a free plan
- No free plan
Keep KumoMTA, or make your own?
Keep it
To replace KumoMTA you would be making mail servers with a good name among inbox providers. That is not a weekend's work, with an AI app builder or without one.
That makes this kind of software worth paying for, not this one in particular: 26 of the 50 other email sending services grade higher. It costs $5,000 a year. KumoMTA is open source, so there is a third way: take its code and run it yourself.
What you could not
- Mail servers with a good name among inbox providers.
- A real app for Linux. Something home-made would be a web page.
- It plugs into other products, Kafka, AMQP and Prometheus among them, and has an API.
- The depth: we grade its features B, which means it covers the whole job.
What this rests on. KumoMTA’s listing: what it does, where it runs, what it plugs into and what it costs. It is a judgement about the kind of software this is. We have not built a replacement for it, and making your own means looking after it too. How we decide, and every tool’s verdict.
What is KumoMTA?
KumoMTA is an open-source mail transfer agent for enterprises and high-volume senders that run their own sending infrastructure. It is configured with Lua scripting and can connect to webhooks, AMQP, Kafka, Vault, Prometheus and Grafana. The software is free; the vendor sells support as yearly sponsorships priced by message volume.
Worth knowing
- It is software you run yourself on your own servers; the pages do not say which operating systems are supported.
- Support is priced per billion messages a year with no server limit; Silver is business hours only, and Enterprise has no published price.
- Configuration is done in Lua scripting, so it suits engineers, not a point-and-click setup.
Key features
- High-volume sending
- The vendor says a single server can send several million messages an hour, and that it can scale out with Docker and Kubernetes.
- Lua policy scripting
- Behavior is set in Lua scripts, with policy helpers for common configurations.
- Integrations for operations
- Supports webhooks, AMQP, Kafka, Vault, Prometheus, Grafana and direct database access.
- Traffic shaping and IP pools
- A customer quote on the site names traffic shaping and IP pool automation as the parts it builds on.
- Migration guides
- The site has a migration center with pages for moving from Momentum, PowerMTA, Halon, SendGrid and Hurricane MTA.
- Open source
- Released under the Apache 2 license, with the source code on GitHub.
KumoMTA pricing
As of Nov 13, 2026, KumoMTA has a free plan, and paid plans start at $5,000 per billion messages per year for Silver support.
- Starts at
- $5,000 per billion messages per year for Silver support
- Free plan
- The software and all its features are free under the Apache 2 license; community support runs through a Discord server.
- Free trial
- None listed
| Plan | Price | What you get |
|---|---|---|
| Community | $0 | Free software with every feature. Help comes from the community Discord server; you host it yourself. |
| Silver | $5,000per billion messages per year | Business-hours support (9-5 US Eastern) by email and portal, a shared sponsor Discord channel and help with basic configuration. |
| Gold | $10,000per billion messages per year | Support 8-7 US Eastern, a 24/7 critical-issue SLA, a private Discord and help with custom Lua policy. |
| Enterprise | Custom | 24/7/365 support, telephone support, a private Discord or Slack channel and refactored policy scripts. No price is stated; contact the vendor. |
Read from kumomta.com on Nov 13, 2026. Prices change, so confirm with KumoMTA before you buy.
Works with
- Kafka
- AMQP
- Prometheus
- Grafana
- Vault
- Docker
- Kubernetes
KumoMTA alternatives
- KumoMTA vs MailerQ
Free trial · from €10,000 one-time
- KumoMTA vs MailChannels
Free plan · from $10/mo
- KumoMTA vs Bird Email
Free plan · from $15/mo
- KumoMTA vs AhaSend
Free plan · from $10/mo
Common questions
Does KumoMTA have an Android app?
No Android app was listed when its pages were read on Nov 13, 2026. KumoMTA is listed for Linux.
Does KumoMTA have an iPhone app?
No iPhone app was listed when its pages were read on Nov 13, 2026. KumoMTA is listed for Linux.
Is KumoMTA open source?
Yes. KumoMTA is open source, according to its own site. It can also be run on a server of your own.
Does KumoMTA have an API?
Yes. KumoMTA offers a public API, according to its own site.
Sources for this page
The prices, plans, platforms and features above were read from these pages on Nov 13, 2026.