$ dig +short mx inboxtooling.com

Email infrastructure
diagnostics & tools

Test inbox placement, audit DNS records, troubleshoot deliverability. Built for mail operators, deliverability engineers, and KumoMTA users.

MX Lookup

SPF Checker

DKIM Validator

DMARC Analyzer

Inbox Tester

Enter a domain to look up MX records

Your email toolkit

Everything you need to diagnose, monitor, and optimize email delivery

Inbox Placement Test

Send test emails to seed accounts across major providers and see where your messages land — inbox, spam, or missing.

DNS Record Audit

Comprehensive checks for MX, SPF, DKIM, DMARC, PTR, and BIMI records. Spot misconfigurations before they hurt delivery.

Blacklist Monitor

Check your IPs and domains against 100+ DNSBLs. Get alerts when you land on a list so you can act fast.

SMTP Diagnostics

Connect to any mail server and inspect the SMTP conversation. Test STARTTLS, authentication, and banner responses.

Deliverability Score

Aggregate analysis of your sending domain health. SPF alignment, DKIM strength, domain age, and reputation signals.

Header Analyzer

Paste raw email headers and trace the full delivery path. Identify delays, authentication results, and routing hops.

Built for KumoMTA

We specialize in KumoMTA — the high-performance, policy-driven MTA built in Rust. Whether you're migrating from PowerMTA, setting up a fresh deployment, or tuning your Lua policies, we've got you covered.

Installation guides & deployment playbooks
Lua policy configuration examples
Performance tuning & queue management
Migration paths from PowerMTA / Postfix
Log parsing & analytics integration
Community support via Telegram

-- shaping.lua: per-domain throttle policy
local kumo = require('kumo')

kumo.on('get_queue_config', function(domain)
  return kumo.make_queue_config({
    max_connection_rate = '100/min',
    max_message_rate   = '50/s',
    max_deliveries_per_connection = 100,
    idle_timeout       = '60s',
  })
end)