First send via SMTP

You need

• A project with a connected domain and an approved sender address.
• An SMTP credential for that project: a username and a password shown once. SMTP credentials only send; they can’t call the API.
• The SMTP host name shown on the project’s SMTP page.

Settings

Setting	Value
Host	shown in your dashboard
Port	587 with STARTTLS, or 465 with implicit TLS
Encryption	required, TLS 1.2 or newer; keep certificate verification on
Authentication	PLAIN or LOGIN, only after TLS
From	must exactly match your approved sender address

Example with Nodemailer

import nodemailer from 'nodemailer';

const transport = nodemailer.createTransport({
  host: process.env.WENEED_SMTP_HOST,
  port: 587,
  secure: false, // STARTTLS is negotiated on 587; use 465 with secure: true for implicit TLS
  requireTLS: true,
  auth: { user: process.env.WENEED_SMTP_USER, pass: process.env.WENEED_SMTP_PASS },
});

await transport.sendMail({
  from: 'Your App <hello@yourdomain.com>',
  to: 'person@example.com',
  subject: 'Welcome',
  text: 'Thanks for signing up.',
  headers: { 'X-Email-Idempotency-Key': 'signup-7f3c2a91-welcome' },
});

A 250 reply means the message is stored and queued, not delivered.

Avoid duplicates

Ordinary mail clients retry on their own. If the connection drops after you sent the message but before the 250 arrived, a retry can create a second message. Add the X-Email-Idempotency-Key header (16 to 128 printable characters) so a retry of the same message is recognised. See Retries and duplicates.

What SMTP doesn’t do

One recipient per message, no attachments, and no sent folder or inbox. Full limits are in the SMTP reference.