SMTP for SaaS — Transactional + Marketing in One Stack

Connect Amazon SES or Postmark for transactional, and RAPID SMTP for product announcements, onboarding sequences, and customer newsletters. One contact database, two senders, no per-email fee.

The problem for SaaS founders

Per-email pricing on SendGrid/Mailchimp scales worse than your MRR.
Onboarding flows live in product code; newsletters live in a marketing tool.
Sender reputation gets split across multiple ESPs.

How RAPID SMTP solves it

Unified contact list

Sync users from your app via the REST API. Same contact row gets product emails and marketing emails.

Two SMTP profiles

Add SES for transactional (cheap, fast) and a warm-up SMTP for marketing. RAPID SMTP routes based on campaign type.

Webhook events

Bounces, complaints, and unsubscribes feed back into your app via webhooks.

Setup in 5 steps

Sign up for RAPID SMTP and add your Amazon SES SMTP credentials.
Verify your sending domain (SPF, DKIM, DMARC) — we walk you through it.
Import your user list via CSV or the REST API.
Create a transactional template and a marketing template.
Wire your app's `POST /api/email` calls to RAPID SMTP's relay endpoint.

Code snippet

await fetch("https://smtp.rapidhostbd.com/api/v1/send", {
  method: "POST",
  headers: {
    Authorization: `Bearer ${process.env.RAPID_SMTP_KEY}`,
    "Content-Type": "application/json",
  },
  body: JSON.stringify({
    to: "user@example.com",
    template: "welcome",
    variables: { name: "Sadia" },
  }),
});

Recommended SMTP providers

Amazon SES
Postmark
Mailgun

FAQ

Can I separate transactional and marketing in RAPID SMTP?

Yes — add two SMTP accounts and assign each campaign or template to the correct one.

Do you have a Node.js SDK?

We expose a REST API and SMTP relay; any HTTP client or nodemailer-compatible SMTP works.