Transactional email that just works
Power signups, password resets, invoices, and product notifications with a clean Email API, reliable SMTP relay, and inbox-first deliverability. Built for SaaS and product teams that can't afford email outages.
Transactional email is the plumbing of your product: account creation, login links, security alerts, billing receipts, and lifecycle events. If those messages don't land, users churn, support tickets spike, and trust erodes instantly.
Cllavio gives you a straightforward transactional email service with an Email API, SMTP relay, and a UI your teammates can actually use — without the bloat of an all-in-one marketing suite. You get logs, suppression rules, and deliverability guardrails instead of surprise limits and hidden switches.
Use the same infrastructure for both transactional and light lifecycle campaigns, or keep them separated by domain and sender while managing everything in one place.
Clean Email API
Simple JSON + multipart requests to send transactional emails from your backend or serverless functions. Responses are predictable, errors are explicit, and tokens are bound to senders.
SMTP relay when you need it
Drop in SMTP credentials for legacy systems or third-party tools that can't call an API yet. Same deliverability stack, same domain authentication, one place to review logs.
Logs, bounces, and reputation
See what was sent, which mailbox provider received it, and why a message bounced. Track hard bounces and protect your domains with automatic suppression rules.
How Cllavio works as your transactional email service
1. Connect your domain
Add SPF, DKIM, and DMARC for your sending domain or subdomain. Cllavio generates the DNS records and verifies them in a few minutes.
You can keep corporate email on the root domain and run product notifications on a subdomain like mail.yourdomain.com.
2. Create senders & tokens
Add sender addresses such as no-reply@mail.yourdomain.com and billing@mail.yourdomain.com, then generate API and SMTP credentials bound to those senders.
Tokens are scoped so one compromise doesn't give access to every sender you own.
3. Send via API or SMTP
Use the Email API to trigger emails on events (signup, reset, invoice generated, subscription changed), or configure SMTP in tools that only speak SMTP.
You can mix both: API for core product flows, SMTP for legacy apps, CRMs, or billing tools.
4. Monitor logs, bounces & metrics
Review delivery status, hard bounces, and engagement. Use this data to clean your lists and keep your transactional traffic healthy.
Cllavio automatically suppresses hard bounces and can pause dangerous traffic patterns before ISPs punish your domain.
Typical transactional flows you can power with Cllavio
Account & security
- Signup confirmations and welcome emails
- Password resets and magic login links
- Two-factor auth and security alerts
- Device and location change notifications
Billing & product
- Invoices, receipts, and payment failures
- Subscription renewals and plan changes
- Usage alerts (overages, quota thresholds)
- Feature announcements and status updates
Example: send a transactional email via API
This is a simplified example. See the full spec in the Email API docs.
POST https://api-marketing.cllavio.com/api/v1/emails
X-Api-Access-Token: <ACCESS_TOKEN_BOUND_TO_SENDER>
X-Api-Secret-Token: <SECRET_TOKEN_BOUND_TO_SENDER>
Content-Type: multipart/form-data
payload = {
"from": "no-reply@mail.yourdomain.com",
"to": ["user@example.com"],
"subject": "Your password reset link",
"body": "<p>Click here to reset your password: {{reset_link}}</p>",
"textBody": "Reset your password: {{reset_link}}"
}The from address must match a verified sender, and tokens must be created for that sender.
If most of your revenue comes from your app, treat transactional email as infrastructure, not an afterthought. Start with a dedicated sending domain, wire up your core flows, then monitor logs for a few weeks before moving 100% of your traffic.
Want help planning the switch from your current provider? Contact support@cllavio.com and we'll review your current setup and migration plan.
Ready to build? Start with the Email API docs or domain setup guide.