Email infrastructure that your team doesn't have to babysit.
Coastar LNC handles authentication, reputation, list hygiene, and delivery — so your engineers can focus on shipping the product. Send your first transactional email in under five minutes with our API, or bring your existing pipeline. Transactional email only — strict on bad and unsolicited email.
600,000
Transactional emails sent · 24 Oct 2026Source: Coastar LNC platform telemetry · Last updated 24 Oct 2026
Six capabilities. One platform.
Everything you need to send transactional email reliably, with the tools to prove it's working — and the enforcement to keep bad senders out.
Transactional sending API
A single POST endpoint, REST and SMTP, with idempotency keys and structured error handling. SDKs for Node, Python, Go, PHP, and Ruby. Transactional sends only.
AI deliverability engine
Four continuously running models score every message, optimize send times, and flag risky addresses before they bounce.
Real-time analytics
Delivery, bounce, complaint, and engagement metrics updated every minute. Every number has a source and a timestamp.
Enterprise infrastructure
Redundant sending infrastructure, with SPF, DKIM, and DMARC configured on every domain by default.
Automatic suppression
Bounce and complaint events are processed automatically, and bad addresses are removed before the next send. There is no path around the suppression list.
Webhooks & event streams
Every delivery, bounce, complaint, open, and click fires a webhook. Stream events to your own warehouse.
Strict on bad email. Transactional only.
Coastar LNC is engineered around a simple rule: transactional email only. Every mechanism below exists to keep bad and unsolicited email off the platform.
What we accept
- Receipts, invoices, and payment confirmations
- Password resets and account verification
- Order and shipping notifications
- Security and login alerts
- Status and lifecycle notifications the recipient triggered
What we do not accept
- Marketing, promotional, or newsletter email
- Purchased, rented, scraped, or harvested lists
- Cold outreach or unsolicited sending
- Any send that ignores a suppression or unsubscribe
- Any send that pushes bounce or complaint rates above industry thresholds
The AI is in the sending path, not on the marketing page.
Coastar LNC's AI layer runs on every message before it leaves our platform. It scores, times, and filters — and it improves continuously based on real engagement data from your own sending.
The models are per-account, not global. Your subject-line scorer learns from your subscribers' behavior, not someone else's.
The four models
- Subject-line scoring — flags high-risk phrasing, spam-trigger words, and low-engagement patterns before sending.
- Send-time optimization — picks the highest-engagement send window per recipient, based on historical open data.
- List hygiene scoring — predicts which addresses are most likely to bounce and suppresses them pre-emptively.
- Anomaly detection — watches bounce, complaint, and volume rates and alerts you before reputation is affected.
Send your first email in under five minutes.
One endpoint, one key, and one JSON payload. Idempotency, retries, and delivery events are handled for you.
/v1/emails
{
"from": "[email protected]",
"to": ["[email protected]"],
"subject": "Your receipt from Example App",
"html": "<p>Thanks for your order.</p>",
"idempotency_key": "order_1042",
"tags": ["receipt", "production"]
}
Developer-first, out of the box
- REST and SMTP, both production-ready
- Idempotency keys for exactly-once delivery
- Structured error responses (JSON, machine-readable)
- SDKs for Node, Python, Go, PHP, Ruby
- Webhooks for every delivery event
- Free sandbox with your own domain
- 99.99% uptime SLA on paid plans
What you get that others charge extra for.
AI included
Subject-line scoring, send-time optimization, and list hygiene are on every plan — not an enterprise upsell.
Real metrics
Every number on our dashboard has a source and a timestamp. No marketing roundups, no inflated claims.
Transparent pricing
Flat per-email pricing, no per-seat charges, no surprise overage fees. See our pricing page.
Start with a free sandbox.
Bring your own domain, send test emails, and see the dashboard before you pay anything. Transactional senders only.
Get Started