Deliver transactional emails with unmatched deliverability, real-time insights, and developer-first APIs. Built with authenticity. Designed for scale.
Enterprise-grade
Security & Compliance
Developer-first
APIs & SDKs
High Deliverability
99.9% Inbox Rate
Real-time Insights
& Analytics
Compliance & Security
POST https://api.stacksender.com/v1/emails
Authorization: Bearer cl_live_xxx
Content-Type: application/json
{
"from": "Acme <noreply@acme.com>",
"to": "user@domain.com",
"subject": "Welcome to Acme",
"text": "Hello from StackSender!"
}{
"id": "email_8f3c2b",
"status": "delivered",
"message": "Email queued successfully"
}Developers & Teams
Emails Sent
Countries Reached
Inbox Delivery
Uptime
Trusted by innovative companies
Every feature below is included on every paid plan. Comparable tooling assembled from other vendors runs into the hundreds per month.
Your IDE catches missing variables before deploy.
Live in stacksender/define. Declare each email's variable shape once with defineEmail<{...}>(). Missing or typo'd fields fail at the TypeScript boundary; CI rejects the PR. The only email provider with end-to-end compile-time safety.
npx ep dev — every send appears in a local mailbox.
Live in npx ep dev. Boots a localhost mailbox at port 8025 with a polished dark-mode UI. Set EP_DEV_INBOX_URL and the SDK auto-routes — staging never leaks an email to real recipients again.
Every PR gets its own isolated environment.
Live at POST /api/v1/sandboxes. CI calls our endpoint with a branch name; we return a key prefixed re_sbx_ that bypasses billing, ignores production suppressions, and auto-revokes when the branch is deleted. Idempotent — same branch gets the same key on retries.
Seed accounts at every major provider. No third-party tool.
Live in /dashboard/placement. Submit a subject, we fan out to Gmail / Outlook / Apple / Yahoo / Proton seed mailboxes and return placement (Inbox · Updates · Promotions · Spam) plus a 0–100 score in seconds. Free tier: 2/mo · Pro: 10/mo · Scale: 50/mo.
Spam score, accessibility, dark-mode, mobile — in one report.
Live now in the template editor. Eight deterministic checks plus optional GPT-4o-mini suggestions: spam triggers, Flesch reading level, alt-text coverage, link density, mobile rendering, dark-mode pitfalls, plain-text fallback, and CAN-SPAM unsubscribe compliance. Free track works without any AI key.
Set a monthly limit. We pause before you blow it.
Live now in Billing. Set a hard monthly USD cap with 50/75/90% email alerts and automatic pause-at-limit — sends return 402 cost_cap_reached until the next period. The only email API that won't let your invoice surprise you.
Recipients pick what they want, not just all-or-nothing.
Live now in Settings → Preferences. Define your own categories (receipts, digest, marketing) and recipients choose per category from a hosted preference center. Tag any send with category: "slug" and we filter opt-outs at the API layer.
0–100 score, refreshed daily, drill into anything red.
Live now under Domains → Health. A single 0–100 score per sending domain built from DKIM/SPF/DMARC validity, 5-RBL cleanliness, complaint rate, bounce rate, and active-sender signals. Recomputed every 24 hours plus on-demand recheck.
Comparable vendors charge $300+/mo. We bundle all eight on Pro for $25/mo.
The send endpoint is a thin layer over enterprise SMTP. Idempotency keys de-dupe replays. Detailed timing headers come back on every response so you can measure the path yourself.
A familiar, well-documented HTTP surface. Send single, batch, or scheduled emails. Migrate from any provider in an afternoon.
Automatic DKIM, SPF, and DMARC. Bounce, complaint, and suppression handling. We protect your sender reputation.
Catch typos, disposable domains, and dead inboxes before they bounce. Risk-scored, cached MX lookups.
Reusable HTML templates with clean variable substitution. Versioned, previewable, testable from the dashboard.
Signed HTTPS callbacks for delivered, opened, clicked, bounced, and complained events. Replay and retry-with-backoff.
Catch-all inbox routes and per-alias forwarding rules with SRS rewriting. Spin up support@ in two clicks.
Start free. Upgrade when your product is live. Pay for what you actually send.
Drag to estimate · emails / mo
Free
For evaluating the platform on a side project.
$0/mo
3,000 emails / mo
Pro
For shipping production apps.
$25/mo
50k emails / mo
Scale
For high-volume senders & growing teams.
$75/mo
200,000 emails / mo
Enterprise
For volume above 500k / mo or compliance needs.
Custom
Tailored to your needs
Every plan includes DKIM, SPF & DMARC, delivery & bounce tracking, webhooks, and the full REST API. Cancel any time. No surprise overage fees.
Eight things, bundled in: end-to-end TypeScript-typed email schemas, a real localhost dev inbox via npx ep dev, automatic per-branch sandbox API keys, free inbox-placement testing across Gmail/Outlook/Yahoo/Apple/Proton, an AI pre-send deliverability advisor, hard monthly cost caps with auto-pause, categorical (not all-or-nothing) unsubscribe, and a daily 0-100 domain health score.
We charge $0.10 per 1,000 emails on paid plans — typically 60-75% less than mainstream alternatives once you cross 50,000 emails per month. Free tier covers 3,000 / mo with no credit card.
Yes. Our REST shape is intentionally compatible with the conventions developers already know — base URL, send command, webhook payload. In most cases a search-and-replace is enough.
Enterprise SMTP infrastructure with automated DKIM key rotation, SPF & DMARC alignment, complaint feedback loops with major ISPs, and a shared-IP pool that's continuously warmed.
We support both transactional (priced per email) and marketing (priced per contact). One unified dashboard, one API, one bill.
Not yet — we're a new platform and won't promise an uptime number we haven't measured. The /status page runs live health checks every 60 seconds. A formal SLA with credit-back is on the roadmap.
3,000 emails per month, free forever. No credit card. The dashboard takes about five minutes to wire up.