Open source libraries
Prebuilt libraries and sample code for popular languages — integrate transactional or bulk sending in minutes.
01 email API
Send with an API that outpaces traditional SMTP.
APIs process requests faster than a classic SMTP server — which matters when you send millions of emails. Scale from 10 to 3,000,000+ sends with 99.9% uptime.
IPv4 Dedicated pools. Domain-level reputation you control — not a shared neighbourhood.
Metrics Delivered, bounced, deferred as they happen. SMTP and API, same path.
Relay STARTTLS on 587, or the HTTP API. Transactional and bulk on one set of credentials.
Everything you need to integrate email fast.
Reliable, scalable infrastructure
User-friendly SMTP integration and RESTful APIs scale to any volume while guaranteeing 99.9% reliability and uptime.
Specialists on call
Our API specialists understand your technical needs quickly and help you find the source of any problem — free, on chat, Mon–Fri 07:30–16:30 GMT+2.
SMTP relay or email API — which should you use?
SMTP relay
The universal protocol — works with any CMS, CRM, or legacy system.
- ✓ Point existing software at our secure servers
- ✓ No code changes for simpler applications
- ✓ Full deliverability tooling included
- ✕ Slower per-request than the API at huge volume
Email API Faster
RESTful endpoints built for products sending millions of emails.
- ✓ Processes requests faster than traditional SMTP
- ✓ Libraries in pretty much every language
- ✓ Personalization with Handlebars or Golang templates
- ✓ Webhooks for bounces and delivery events
Personalize every email.
Use Handlebars 3.0 or Golang personalization tokens in your templates for fully customizable content — or build visually with Passport, our drag-and-drop email designer with dynamic images and real-time team collaboration.
How do you install and connect SMTP-X?
Most customers connect in under five minutes. Choose SMTP credentials for existing software or REST API keys for custom applications.
Create your account
Sign up free and add your sending domain in the dashboard.
Add DNS records
Copy SPF, DKIM, and tracking CNAME values to your registrar. See the multiple domain guide for details.
Verify the domain
Wait for DNS propagation (up to 48 hours). The dashboard confirms when verification succeeds.
Connect SMTP or API
Use hostname, port 587 (STARTTLS) or 25 and 2525, and credentials from SMTP settings — or authenticate REST requests with your API key.
Need hands-on help? Support includes free setup assistance — contact us Mon–Fri 07:30–16:30 GMT+2.
Start sending with the email API in minutes.
Integrating email into your product doesn't have to be a pain — whether it's transactional or bulk.
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