Transactional API + Deliverability + Builder

Email that lands. Pay only for what you send.

A transactional email API, real deliverability tooling, and a visual template builder in one platform. 3,000 emails a month free, then $0.40 per 1,000 — no subscription, no contact tiers.

99.2% inbox placement
3,000 free / month
<200ms API p50
mailstack — activity Live
A Your receipt from Northwind ava@northwind.io Delivered
L Verify your email address liam@acme.dev Opened
M Reset your password mia@loopwork.co Delivered
N Welcome to Beacon 👋 noah@beacon.app Delivered
Z Your weekly digest is ready zoe@tidepool.io Opened
99.2%
delivered
142ms
p50 send
0
bounces
Send your first email
curl https://api.mailstack.voostack.com/v1/emails \
-H "Authorization: Bearer ms_live_…" \
-d '{"from":"hi@you.com","to":"u@dev.com","subject":"Hi","text":"Hello!"}'
Three products, one platform

The all-in-one email stack.

Resend's API ergonomics, SendGrid-grade deliverability, and Mailchimp's template builder — without stitching three vendors together or paying three bills.

01 / Transactional API

Send through one clean API

POST a single email or a batch of up to 100 and get back a message id you can poll for status. Bearer-token auth with ms_live_ keys, predictable JSON, and 202-on-accept ergonomics developers expect.

02 / Deliverability

Land in the inbox by default

Easy DKIM, aligned SPF and a custom MAIL FROM subdomain, automatic suppression of bounces and complaints, and event webhooks. The reputation plumbing is handled so your mail actually arrives.

03 / Visual builder

Design email without code

A drag-and-drop template builder your whole team can use. Version templates, render them by id from the API, and keep marketers and engineers working from the same source.

Built for production

Everything you need to send at scale.

Read the docs →

Usage-only pricing

3,000 emails/month free, then $0.40 per 1,000. No plan tiers, no contact-count billing, no minimums — you pay for sends and nothing else.

Batch sending

POST /v1/emails/batch accepts up to 100 emails per request with per-item validation and results, so high-volume jobs stay one round-trip.

Domain verification

Add a domain, get the exact DNS records to publish, and hit the verify endpoint to confirm DKIM, SPF, and DMARC alignment.

Automatic suppression

Hard bounces and complaints are suppressed automatically and enforced before a send leaves the queue — protecting your sender reputation.

Hard spend caps

Set a per-organization monthly spend cap. When projected overage hits the cap, sending pauses — no surprise bills, ever.

Message status lookup

GET /v1/emails/{id} returns the full lifecycle of a message: queued, sent, bounced, or failed, with the provider message id.

Trusted by builders

"We replaced three email vendors with MailStack and cut our bill in half. The deliverability just worked."

— Engineering lead, early-access customer
NorthwindAcme CloudLoopworkBeaconTidepool
Simple, usage-only pricing

Pay only for what you send.

3,000 emails free every month, then just $0.40 per 1,000. No plan tiers, no contact-count billing, and a hard spend cap so you're never surprised. Drag the slider to see your bill.

Usage calculator
50,000 emails / month
$18.80 /mo
Free
3,000
Billable
47,000
Blocks ×1k
47

3,000 emails free each month, then $0.40 per 1,000 (billed per 1,000, rounded up). No subscription.

Send your first email today.

Grab an API key, add your domain, and you're sending in minutes. The first 3,000 emails each month are on us.