Send email over SMTP: point any app at Zend

Not everything that needs to send email can call an API. Your CMS, your CRM, your helpdesk, the invoicing tool someone wired up three years ago, even an office printer. A huge amount of software knows exactly one way to send mail: SMTP. Until now, connecting any of it to Zend meant building a bridge. Today it means changing four settings.

Zend now speaks SMTP.

The same send, a different front door

The important part is what doesn't change. A message sent over SMTP doesn't take a shortcut around the things that actually get mail into the inbox. It runs through the exact same path as a POST /email/send call:

• It has to come From a domain you've verified, or it's rejected; no half-authenticated mail leaks out.
• It's signed with DKIM and sent over SPF-authorized, reputation-monitored infrastructure.
• Deliveries, bounces, and complaints show up in the same Email history, and the same suppression list keeps your reputation clean.
• It draws on the same email plan and the same credits.

SMTP is simply a second door onto that path. Whatever you plug in inherits the deliverability work you'd get from the API, for free.

Your API key is the password

There's no new credential to manage. You authenticate with the same API key you'd use for the API, the one with the email:send scope. The only quirk is that the username is a fixed value, the literal word zendsmtp, and your key goes in the password field.

Your key is only accepted over TLS, so the connection is encrypted before the key ever crosses the wire.

Sending, from anything

In most tools this is a settings screen. In code it's a few lines:

import nodemailer from "nodemailer";

const transport = nodemailer.createTransport({
  host: "smtp.tryzend.com",
  port: 587,
  auth: { user: "zendsmtp", pass: process.env.ZEND_API_KEY },
});

await transport.sendMail({
  from: "receipts@yourdomain.com",
  to: "customer@example.com",
  subject: "Your receipt",
  html: "<h1>Thanks for your order</h1>",
});

To, Cc, and Bcc all behave the way you'd expect. Each recipient is delivered, tracked, and billed as its own message, so a note to three people is three lines in your history, each with its own delivery status.

When to reach for it

If you're writing new code, the Email API is still the richest way to send: structured responses, per-message IDs, everything in one call. SMTP is for everything else: the software you didn't write, can't change, or would simply rather not. Point it at Zend, verify your domain, and it inherits the same deliverability the rest of your mail already has.

Full setup is in the SMTP docs.