StackSender is the email infrastructure platform that helps modern teams engage customers with confidence at any scale.
Every feature below is available without a monthly platform fee. 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. Launch access: 2/mo · grandfathered Pro: 10/mo · grandfathered 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.
Configure for free, then purchase prepaid credit only when you choose to send.
$0to start
Build the integration, create API keys, and verify domains without a platform subscription.
$0.40/ 1,000 recipients
Managed sending is awaiting production access and live tenant acceptance and cannot be purchased yet.
Purchase only when you choose. Exact packs: $5, $10, $25, $50, $100, $250, or $500.
Create an account →No fixed forwarding fee. Buy processing credit when you need it.
$8
10,000 forwards
Prepaid processing credit
$70
100,000 forwards
Prepaid processing credit
$600
1,000,000 forwards
Volume review required
Large-message data: $0.75/GiB, metered pro rata. Existing subscriptions retain only their explicitly grandfathered terms.
All available sending includes DKIM, SPF and DMARC guidance, delivery and bounce tracking, webhooks, and the REST API. Purchased prepaid credit never expires while your account remains open; promotional credit expires 30 days after grant. No automatic reloads.
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.
Get $1.20 in one-time promotional service credit after verifying a domain and payment method—enough for up to 3,000 StackSender-managed recipients at the published rate. Configure your account and domain for free. You only use StackSender and your DNS provider; you never need an AWS account, AWS credentials, or separate AWS billing. Your card is required before the first live send and is not charged unless you explicitly purchase prepaid credit. Managed sending remains waitlist-only until production access and live tenant acceptance are complete. No monthly platform fee. Purchased prepaid credit never expires while your account remains open. Promotional credit expires 30 days after it is granted.
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.
We build on Amazon SES. Domains are authenticated with DKIM (SES-managed keys) plus SPF and DMARC alignment, bounce and complaint feedback is consumed automatically, and any address that hard-bounces or complains is suppressed from all future sends.
Transactional sending is the focus. Broadcasts to an audience you own are supported and billed per email like everything else — we do not accept purchased, rented, or scraped lists.
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.
Configure your account and DNS for free. Managed sending opens only after production access and live tenant safety checks are complete. No monthly platform fee.