SMTP Service

Send transactional email through DirectIQ from any application, framework or service that supports SMTP. No code changes are needed beyond your mail settings: point your SMTP client at DirectIQ and sign in with your API key.

Email sent over SMTP goes through the same pipeline as the Transactional Emails API. It uses the same credits, sender rules and reporting.

Connection settings

Setting	Value
Host	`smtp.directiq.com`
Port	`587` (STARTTLS, recommended) or `465` (TLS)
Encryption	Required
Authentication	`PLAIN` or `LOGIN`
Username	`api`
Password	Your X-API-Key
Maximum message size	25 MB, including attachments

You can find your X-API-Key and these settings in DirectIQ under Integrations → SMTP.

🚧
Encryption is required
The server offers authentication only on an encrypted connection. On port 587, your client must issue STARTTLS before it signs in. On port 465, the connection is encrypted from the start.

Before you send

Use a confirmed sender. The From address must be a sender confirmed in your account. See Senders.
Have credits available. Each recipient in To uses one transactional send.
Keep your key private. The SMTP password is your X-API-Key. If you regenerate it on the API Keys page, update your SMTP settings too.

Examples

Node.js (Nodemailer)

import nodemailer from "nodemailer";

const transporter = nodemailer.createTransport({
  host: "smtp.directiq.com",
  port: 587,
  secure: false, // upgrades to TLS with STARTTLS
  auth: {
    user: "api",
    pass: process.env.DIRECTIQ_API_KEY,
  },
});

await transporter.sendMail({
  from: '"Acme" <[email protected]>',
  to: "[email protected]",
  subject: "Your order has shipped",
  html: "<p>Your order <strong>#1042</strong> is on its way.</p>",
});

Python

import os
import smtplib
from email.message import EmailMessage

msg = EmailMessage()
msg["From"] = "Acme <[email protected]>"
msg["To"] = "[email protected]"
msg["Subject"] = "Your order has shipped"
msg.add_alternative("<p>Your order <strong>#1042</strong> is on its way.</p>", subtype="html")

with smtplib.SMTP("smtp.directiq.com", 587) as smtp:
    smtp.starttls()
    smtp.login("api", os.environ["DIRECTIQ_API_KEY"])
    smtp.send_message(msg)

PHP (PHPMailer)

use PHPMailer\PHPMailer\PHPMailer;

$mail = new PHPMailer(true);
$mail->isSMTP();
$mail->Host       = 'smtp.directiq.com';
$mail->Port       = 587;
$mail->SMTPSecure = PHPMailer::ENCRYPTION_STARTTLS;
$mail->SMTPAuth   = true;
$mail->Username   = 'api';
$mail->Password   = getenv('DIRECTIQ_API_KEY');

$mail->setFrom('[email protected]', 'Acme');
$mail->addAddress('[email protected]');
$mail->isHTML(true);
$mail->Subject = 'Your order has shipped';
$mail->Body    = '<p>Your order <strong>#1042</strong> is on its way.</p>';

$mail->send();

C# (MailKit)

using MailKit.Net.Smtp;
using MailKit.Security;
using MimeKit;

var message = new MimeMessage();
message.From.Add(new MailboxAddress("Acme", "[email protected]"));
message.To.Add(MailboxAddress.Parse("[email protected]"));
message.Subject = "Your order has shipped";
message.Body = new TextPart("html") { Text = "<p>Your order <strong>#1042</strong> is on its way.</p>" };

using var client = new SmtpClient();
await client.ConnectAsync("smtp.directiq.com", 587, SecureSocketOptions.StartTls);
await client.AuthenticateAsync("api", Environment.GetEnvironmentVariable("DIRECTIQ_API_KEY"));
await client.SendAsync(message);
await client.DisconnectAsync(true);

cURL

curl --url "smtp://smtp.directiq.com:587" --ssl-reqd \
  --user "api:$DIRECTIQ_API_KEY" \
  --mail-from "[email protected]" \
  --mail-rcpt "[email protected]" \
  --upload-file email.eml

How messages are delivered

One email per To recipient. A message with three addresses in To is delivered as three separate emails. Each one uses a send and gets its own report.
Cc and Bcc are copied on every email in the message. Recipients you add in the SMTP envelope but not in the To or Cc headers are treated as Bcc.
HTML is preferred. If a message has both an HTML part and a plain-text part, the HTML part is sent.
Attachments are supported, within the 25 MB message limit.
At least one address is required in the To header.

Troubleshooting

Problem	What to check
`530 Authentication required`	Sign in before sending. On port `587`, issue `STARTTLS` first.
`535 Authentication failed`	The username must be exactly `api`, and the password must be your current X-API-Key.
`AUTH` not offered	The connection isn't encrypted yet. Use STARTTLS on `587`, or connect with TLS on `465`.
`554 Transaction failed`	No email could be created. Usually the `From` address isn't a confirmed sender, or your account has no credits left.
Connection timed out	Some hosting providers block outgoing SMTP ports. Try the other port, or ask your provider to open it.

📘
Prefer HTTP?
If your platform blocks SMTP ports, or you need idempotency and delivery status, use the Transactional Emails API instead.