Skip to content
MailVitals Email deliverability
EN

Language

Sign in

Beat and the Academy have separate accounts.

Get Beat
The Academy · Advanced

KumoMTA: High-Volume Sending Engine

12-module KumoMTA course: Lua config, listeners, queues, IP warming, DKIM/SPF/DMARC alignment, bounces, FBLs, ClickHouse analytics, and HA sharding.

Start lesson 1See all 25 lessons
12
Modules
25
Lessons
9h
Estimated

Curriculum

12 modules, 25 lessons

Follow them in order or jump to the one you need. Each lesson is its own page, with the next one waiting at the end.

Module 013 lessons

Introduction to KumoMTA

What KumoMTA is, who built it, and where it fits in the modern sending stack.

  1. 01What is KumoMTA?KumoMTA is a dedicated outbound MTA with no mailboxes and no IMAP
  2. 02The MTA landscape and where Kumo fitsThree categories: general-purpose, sending engines, cloud APIs
  3. 03Architecture at a glanceSingle Rust binary, configured entirely in Lua
Module 022 lessons

Installation, Lua Primer & systemd

Get KumoMTA running and learn just enough Lua to find your way around the config.

  1. 04Installing KumoMTADebian 12 is the most-tested target, so start there
  2. 05Just-enough Lua for KumoMTAFive Lua patterns cover almost every KumoMTA config you'll write
Module 032 lessons

Listeners, ESMTP, AUTH & TLS

Configure SMTP listeners, authentication, and TLS termination.

  1. 06Defining listenersMultiple listeners on different ports is normal and idiomatic
  2. 07SMTP AUTH and rate limiting at the listenerAUTH is a Lua callback, so you own the credential lookup
Module 042 lessons

Queues, Scheduling & Traffic Shaping

Per-destination throttling, retry schedules, and queue priorities.

  1. 08Scheduled queues = tenant × destinationScheduled queues key on (tenant, campaign, destination)
  2. 09Traffic shaping with throttlesshaping.toml is hot-reloadable, so you can change rates without a restart
Module 052 lessons

IP Warming Strategies & Pools

Stand up new IPs without burning their reputation.

  1. 10Why warming existsWarming is mandatory for new IPs; expect 3–4 weeks to full volume
  2. 11Egress sources and pools in codeOne egress_source per outbound IP, with matching ehlo_domain + PTR
Module 062 lessons

DKIM Signing, SPF & DMARC Alignment

Get authentication right so your mail isn't filtered before it's read.

  1. 12DKIM signing in KumoMTADKIM signing is one Lua call per message, which makes it easy to do per-tenant
  2. 13Alignment is the only thing that mattersDMARC needs the From-header domain to align with SPF Return-Path OR DKIM d=
Module 072 lessons

Bounce Processing & FBL Handling

Parse bounces, classify codes, and ingest feedback loops.

  1. 14How KumoMTA classifies bouncesBounce classifier turns raw SMTP into actionable categories
  2. 15Feedback Loops (FBL) ingestionRegister FBLs with Microsoft, Yahoo (no Gmail FBL; use Postmaster Tools)
Module 082 lessons

Logging, Hooks & ClickHouse

Stream every event into a queryable warehouse for ops and reporting.

  1. 16KumoMTA's event log structureEvery event is structured JSON, easy to ship anywhere
  2. 17ClickHouse for delivery analyticsClickHouse + KumoMTA = real-time delivery analytics at billions of events
Module 092 lessons

Throttles per Destination (Gmail / Yahoo / M365)

Operator-tuned defaults for the biggest mailbox providers.

  1. 18Gmail's expectations in 2026Gmail: 20 conn/s, 250 msg/s for warm IPs; long pipelines are good
  2. 19Yahoo and Microsoft 365 quirksYahoo: 10 conn/s, 100 msg/s; sign up at Sender Hub for FBL
Module 102 lessons

Suppression Lists & Compliance

Don't send to people who said no, and be able to prove it on demand.

  1. 20What belongs on the suppression listSuppression covers 6 categories, of which unsubscribes are only one
  2. 21One-click unsubscribe (RFC 8058)One-click unsub is mandatory for >5k/day senders since Feb 2024
Module 112 lessons

HA Architecture & Sharding

Scale beyond a single KumoMTA node without dropping queue state.

  1. 22Sharding by tenantNo built-in clustering; shard upstream with consistent hashing
  2. 23Spool durability and node failoverRocksDB spool survives crashes but is local, so node death = stuck queue
Module 122 lessons

Observability, Alerting & Deliverability Tuning

What to measure, what to alert on, and how to keep delivery healthy.

  1. 24Metrics that actually matterPer-destination + per-tenant slicing is non-negotiable
  2. 25Continuous deliverability tuningWeekly review of Postmaster Tools + SNDS + bounce categories
Pulse · cold-email sending

Sending infrastructure that is yours alone.

Every domain gets its own MX host, IP, DKIM selector and certificate. Take it managed, and we run it for you, or buy a licence and run it on your own servers.

Book a demoSee Pulse
# on a fresh Ubuntu server
$ cd pulse && sudo ./install.sh
→ docker compose up · kumomta · stalwart · caddy
→ dashboard ready on https://pulse.yourdomain.com
$

Also from us:Beat: monitoring that tells you the fixConsulting: $65/hr, no retainer