The KumoMTA Insider’s Guide
Everything we know about KumoMTA in one document: what it costs, its grades, getting a refund, getting help and what else to look at. Read it here, or keep a copy.
KumoMTA
The Insider’s Guide
Open-source mail server for high-volume, self-run email sending
Every plan, grade, refund rule and rival among email sending services, read from KumoMTA’s own pages.
Made by Kumo Corp · checked Nov 13, 2026 · toolgpa.com
Contents
- 01WelcomeWhat it is, who it suits, its grades and the ten things to know first
- 02What it costsEvery plan, the free plan, ways to pay less and how prices have moved
- 03What it doesIts main features, where it runs, what it works with and who makes it
- 04Where it standsIts grades against its category, and whether to keep it or make your own
- 05The alternativesThe tools it is most often weighed against, side by side
- 06Quick answersThe questions people ask about it, each answered in a line or two
- 07About ToolGPAWho made this guide, what else is on the site, and how to cite it
ToolGPA put this guide together from KumoMTA’s own pages, its app-store listings and our grades. Every fact in it is on KumoMTA’s page too, where it is kept up to date. Checked Nov 13, 2026.
Part 01 · Overview
Welcome
What it is, who it suits, its grades and the ten things to know first
2.2
GPA, above 14 of the 50 other email sending services we grade
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.
To get you started, here are 9 things to know about KumoMTA, taken from its own pages and our grades.
It's configured in Lua scripting on your own servers, so it suits engineers.
- 1
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.
- 2
Paid plans start at $416.67 a month when paid by the year
As its pricing page puts it: $5,000 per billion messages per year for Silver support.
- 3
There is a free plan
The software and all its features are free under the Apache 2 license; community support runs through a Discord server.
- 4
It runs on Linux
Linux.
- 5
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.
- 6
Lua policy scripting
Behavior is set in Lua scripts, with policy helpers for common configurations.
- 7
Integrations for operations
Supports webhooks, AMQP, Kafka, Vault, Prometheus, Grafana and direct database access.
- 8
A 2.2 GPA, above 14 of 50
That is against the other email sending services we grade, on value, the free plan, features, ease of use and platforms.
- 9
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.
KumoMTA at a glance
- Pricing
- Free plan, from $5,000 per billion messages per year for Silver support
- Free plan
- Yes
- Free trial
- None stated
- Runs on
- Linux
- Made by
- Kumo Corp
- Category
- Email Sending Services
- Our grade
- 2.2 GPA, fair
The report card
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.
| Subject | Grade | Comment |
|---|---|---|
| Value for money | C | The software is free under Apache 2, but you host it yourself, and paid support starts at $5,000 per billion messages a year. |
| Free plan and trial | B | Every feature is free to run, with community help on Discord. You do need your own server to use any of it. |
| Features | B | High-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. |
| Ease of use | D | No store rating on record. It's configured in Lua scripting on your own servers, so it suits engineers. |
| Platforms and integrations | C | Software for your own servers, listed for Linux, with Docker and Kubernetes. No dashboard or hosted version. |
An A is worth 4 points, a B 3, a C 2, a D 1 and an F nothing. The GPA is the average of the five.
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 it 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
Good to know
Good for
- Email platforms and enterprises that want to own their sending infrastructure
- Teams moving off a commercially licensed MTA such as PowerMTA or Momentum
- Engineers comfortable configuring a server with Lua scripts
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.
Part 02 · Pricing
What it costs
Every plan, the free plan, ways to pay less and how prices have moved
$416.67
A month to start, paid by the year. There is a free plan too
KumoMTA has a free plan. Paid plans start at $5,000 per billion messages per year for Silver support.
Every feature is free to run, with community help on Discord.
Community
$0
Free software with every feature. Help comes from the community Discord server; you host it yourself.
Silver
$5,000
per 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
$10,000
per 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.
The free plan
The software and all its features are free under the Apache 2 license; community support runs through a Discord server.
Read from kumomta.com on Nov 13, 2026.
Part 03 · Features
What it does
Its main features, where it runs, what it works with and who makes it
1
Place it runs: Linux
Open-source mail server for high-volume, self-run email sending. Here is what it does, as its own site describes it, and what it covers: open source, self-hostable, public API, transactional email.
High-volume sending, Lua policy scripting, traffic shaping and IP pools, with hooks into Kafka, AMQP, Prometheus, Grafana and Vault.
- 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.
Where it runs
- Linux
What it works with
- Kafka
- AMQP
- Prometheus
- Grafana
- Vault
- Docker
- Kubernetes
KumoMTA is made by Kumo Corp.
Part 04 · Standing
Where it stands
Its grades against its category, and whether to keep it or make your own
14/50
Other email sending services it is graded above
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
- BFree plan and trialAbove 35 of 50
- BFeaturesAbove 30 of 50
- DEase of useAbove 0 of 50
- CPlatforms and integrationsAbove 0 of 50
Price against what you get
Each dot is one of 44 email sending services. Further left costs less; higher up scores better on features, ease of use and platforms. KumoMTA is the marked dot.
What paid plans start at, a month (each step along is roughly double) →
Keep it, or make your own?
Whether this is something you could build for yourself with an AI app builder, and what you would give up.
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.
Part 05 · Alternatives
The alternatives
The tools it is most often weighed against, side by side
MailerQ, MailChannels, Bird Email and AhaSend
The 4 tools KumoMTA is most often weighed against, with where each one differs from it.
- 1.6GPA
MailerQ
Free trial · from €10,000 one-time
Self-hosted mail transfer agent for high-volume email sending.
- KumoMTA has a free plan. MailerQ does not, though it has a free trial.
- Only KumoMTA lists a Linux app.
- Only MailerQ lists a web app.
- 2.8GPA
MailChannels
Free plan · from $10/mo
Email API and SMTP relay for platforms with many downstream senders.
- Only KumoMTA lists a Linux app.
- Only MailChannels lists a web app.
- KumoMTA is open source and self-hostable, according to its own site.
- 2.6GPA
Bird Email
Free plan · from $15/mo
SparkPost's successor: Bird's email API, paid from a prepaid balance.
- Only KumoMTA lists a Linux app.
- Only Bird Email lists a web app.
- KumoMTA is open source and self-hostable, according to its own site.
- 2.4GPA
AhaSend
Free plan · from $10/mo
EU-hosted transactional email API and SMTP relay with a free tier.
- Only KumoMTA lists a Linux app.
- Only AhaSend lists a web app.
- KumoMTA is open source and self-hostable, according to its own site.
Part 06 · Questions
Quick answers
The questions people ask about it, each answered in a line or two
13
Questions, each answered in a line or two
The short version of everything above, for when you only need the answer. Each one is told in full in its part of the guide.
Is KumoMTA free?
KumoMTA has a free plan. The software and all its features are free under the Apache 2 license; community support runs through a Discord server.
How much does KumoMTA cost?
KumoMTA lists 4 plans. Community: $0.
What platforms does KumoMTA work on?
KumoMTA is available on Linux.
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.
Does KumoMTA have an API?
Yes. KumoMTA offers a public API, according to its own site.
What does KumoMTA integrate with?
KumoMTA's listing names Kafka, AMQP, Prometheus, Grafana, Vault, Docker and Kubernetes.
Who makes KumoMTA?
KumoMTA is made by Kumo Corp.
What are the alternatives to KumoMTA?
The closest alternatives to KumoMTA in our directory are MailerQ, MailChannels, Bird Email and AhaSend.
How does KumoMTA compare with other 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.
Is KumoMTA good value for money?
ToolGPA grades KumoMTA C for value for money. 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.
Could I make my own version of KumoMTA?
To replace KumoMTA you would be making mail servers with a good name among inbox providers.
Where this guide comes from
The prices, plans, platforms and features were read from KumoMTA’s own pages on Nov 13, 2026, and the grades were given on Nov 13, 2026. 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.
Every tool we list gets five grades, A to F, each with its reason, and a GPA that averages them. How each is decided is at toolgpa.com/grades. This guide is ToolGPA’s own work; it is not made, paid for or approved by Kumo Corp. Prices change, so check kumomta.com before you buy.
Part 07 · About
About ToolGPA
Who made this guide, what else is on the site, and how to cite it
7,721
Tools graded, in 95 categories
ToolGPA grades software the way a school report grades a pupil: five subjects, a letter for each with the reason written beside it, and a GPA that averages them. Prices, plans and platforms are read from each maker’s own pages and dated, so you always know how fresh a figure is.
Every grade, review and ranking on ToolGPA is our own judgement. No company can pay for a grade or change one. Every tool on the site has a guide like this one, free to download and pass on. It all lives at toolgpa.com.
7,721
tools graded
95
categories
739
price changes on record
579
apps priced in 12 countries
What else is on toolgpa.com
- KumoMTA, kept up to dateEverything in this guide, with prices and grades as they are todaytoolgpa.com/tools/kumomta
- How grades are givenThe rules behind every letter and every GPAtoolgpa.com/grades
- Value chartsWhat each tool costs against what it scores, for every categorytoolgpa.com/charts
- CompareAny two tools side by side, plan by plantoolgpa.com/compare
- Price changesEvery price rise and cut on record, each with its sourcetoolgpa.com/price-changes
- Prices by countryWhat apps cost on the App Store in 12 countriestoolgpa.com/prices-by-country
- Pay lessEvery public discount: yearly billing, students, nonprofitstoolgpa.com/save
- Keep or makeWhich tools are worth paying for, and which you could build yourselftoolgpa.com/keep-or-make
Scan for the live page
Prices and grades as they are today
Quoting this guide?
Please name ToolGPA and link to the live page, so readers can check the figures for themselves:
ToolGPA, "KumoMTA: The Insider's Guide", checked Nov 13, 2026. https://toolgpa.com/tools/kumomta
Know someone choosing between email sending services?
Send them this guide: toolgpa.com/tools/kumomta/guide
ToolGPA elsewhere: youtube.com/@toolgpa
See our other guides
The best-graded email sending services after KumoMTA, each with an Insider's Guide of its own.
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- FluentSMTP Insider's GuideFree WordPress plugin for sending site email through your provider3.2 GPA
- Amazon SES Insider's GuideAWS email sending and receiving, paid per 1,000 emails2.8 GPA
- Forward Email Insider's GuideOpen-source email forwarding and hosting for custom domains2.8 GPA
Choosing software? Every tool graded, every price dated.
Compare tools at toolgpa.com ›Everything in this guide is ToolGPA’s own summary of what KumoMTA’s pages, its app-store listings and public reviews said on the dates shown. Grades are our judgement under the rules at toolgpa.com/grades. Every grade, review and ranking on ToolGPA is our own judgement. No company can pay for a grade or change one. KumoMTA is a trademark of its owner, and this guide is not made, paid for or approved by Kumo Corp. Prices and plans change: check kumomta.com before you buy.