Email infrastructure
that doesn't blink.
Send transactional and marketing email at millions-per-hour scale. One clean API at the edge, a Rust MTA underneath, and deliverability tooling that does the hard parts for you.
1,000 emails/month free · No credit card required
Emails delivered
1,284,331,902
Throughput
48,000/sec
Built for developers
Your first email in under a minute.
A single, predictable REST API. No SDK required — if it can make an HTTPS request, it can send through KubeMail.
- One endpoint for transactional, batch (1,000/request) and broadcasts (100k recipients)
- Idempotency keys with a 24h replay window — retries never double-send
- Signed webhooks for every delivery, bounce, complaint, open and click
- Typed errors with machine-readable codes and field-level validation details
curl -X POST https://api.kubemail.app/v1/emails \
-H "Authorization: Bearer km_live_xxxxxxxxxxxx" \
-H "Content-Type: application/json" \
-d '{
"from": "Acme <hello@acme.com>",
"to": "ada@example.com",
"subject": "Your login code: 482913",
"html": "<p>Your code is <strong>482913</strong></p>"
}'Everything you need to land in the inbox
Throughput and deliverability, not a trade-off.
The control plane runs at the edge. The data plane runs on bare metal. You get the speed of both and the operational burden of neither.
Edge API on 300+ locations
Requests are authenticated, validated and queued at the Cloudflare edge closest to your servers — single-digit-millisecond overhead, wherever you run.
Rust MTA core
Delivery runs on KumoMTA, a Rust engine built for millions of messages per hour per node with predictable memory and latency.
Per-ISP traffic shaping
Connection limits, rates and backoff tuned per mailbox provider. Gmail, Outlook and Yahoo each get exactly the pace they accept.
Dedicated IPs
Enterprise plans get dedicated, warmed IPs with clean PTR records — your reputation is yours alone.
DKIM, SPF & DMARC automation
Keys generated per domain, copy-paste DNS records, live verification and automatic alignment through a custom return-path.
Real-time webhooks & logs
Every event — delivered, deferred, bounced, opened, clicked — streamed to your endpoint, HMAC-signed, and searchable in the log explorer.
Suppression management
Hard bounces, complaints and unsubscribes are suppressed automatically, so you never hurt your reputation by mailing them twice.
iOS app
Delivery health, alerts and logs in your pocket. Know about a bounce spike before your customers do.
Architecture
Edge control plane. Bare-metal data plane.
Your API call never waits on SMTP. Messages are accepted at the edge, queued durably, and handed to a fleet of Rust MTAs that speak each mailbox provider's language.
Edge API
Auth, validation, rate limits & idempotency on Cloudflare Workers
Queue
Cloudflare Queues absorb spikes so your request returns in milliseconds
KumoMTA
Rust MTA: DKIM signing, per-ISP shaping, bounce classification
Inbox
Delivered over warmed IPs with aligned SPF, DKIM and DMARC
Pricing
Simple pricing that scales with you.
Start free. Upgrade when you're ready. Cancel anytime.
Free
For side projects and trying things out.
$0/month
1,000 emails / month
- 1,000 emails per month
- Shared IP pool
- DKIM, SPF & DMARC automation
- Logs, webhooks & suppressions
Pro
For production apps that send every day.
$29/month
50,000 emails / month
- 50,000 emails per month
- $0.0008 per email over quota
- Stripe invoicing & billing portal
- Everything in Free
Enterprise
For high-volume senders who need isolation.
$299/month
500,000 emails / month
- 500,000 emails per month
- Dedicated IP address
- Isolated sender reputation
- Everything in Pro
FAQ
Questions, answered.
Can't find what you need? Reach us at support@kubemail.app.
How fast can I start sending?
Create an account, add your domain, paste four DNS records, and create an API key. Most teams send their first email in under five minutes — DNS propagation is usually the slowest part.
What makes KubeMail fast at scale?
The API runs on Cloudflare's edge and only queues your message, so requests return in milliseconds. Delivery is handled by KumoMTA, a Rust MTA running on bare metal with per-ISP connection and rate shaping.
Do I need to change my existing SPF record?
No. KubeMail uses a custom return-path (bounces.yourdomain.com) as a CNAME, which gives you SPF alignment without touching your root SPF record. You'll also publish a DKIM key and, ideally, a DMARC record.
What happens when I exceed my monthly quota?
Paid plans bill usage beyond the included volume as overage — $0.0008 per email on Pro. The Free plan includes 1,000 emails per month; you can upgrade at any time from the Billing page in your dashboard.
How do you handle bounces and complaints?
Hard bounces and spam complaints are added to your suppression list automatically and future sends to those addresses are dropped. Every event is also delivered to your webhooks and visible in the logs with a plain-English explanation of the SMTP code.
Can I get a dedicated IP?
Yes — Enterprise includes a dedicated IP, warmed gradually and monitored against major blocklists (Spamhaus, Barracuda, SpamCop, SORBS).
Ship email you never have to think about again.
1,000 free emails every month. Upgrade to millions when you need them.