Send with SMTP

Need to send from an app or tool that only speaks SMTP? Point any SMTP client at toSend and your messages flow through the same pipeline — verified domains, suppression handling, logs and analytics all work exactly the same.

We recommend the API

For new integrations, use the REST API instead. It’s faster, returns a message ID with structured responses and richer error handling, and supports batch sending. SMTP is here for compatibility — when you’re wiring up an existing app, a framework mailer, or a third-party tool that only supports SMTP.

Connection details

Setting	Value
Host	smtp.tosend.com
Port	465 (SSL/TLS) or 587 (STARTTLS)
Username	any value (e.g. tosend) — it’s ignored
Password	your toSend API key

You can also find these in your dashboard under Settings → SMTP.

Which port?

Use 465 if your client asks for “SSL/TLS”, or 587 if it asks for “STARTTLS/TLS”. Both are fully encrypted.

If your hosting provider or network blocks the standard ports, use the alternates: 2465 (SSL/TLS) or 2587 (STARTTLS).

Requirements

• An API key — create one under API Keys in your dashboard. The key is used as the SMTP password; the username can be anything.
• A verified sending domain — the From address must use a domain you’ve verified, otherwise the message is rejected.

Keep your key secret

Your API key is a credential. Store it as a secret in your application’s environment — never commit it to source control.

Quick test

Using swaks:

swaks --server smtp.tosend.com --port 465 --tlsc \
      --auth LOGIN --auth-user tosend --auth-password YOUR_API_KEY \
      --from you@your-verified-domain.com --to test@example.com \
      --header "Subject: toSend SMTP test" --body "It works!"

Examples

Nodemailer (Node.js)

import nodemailer from "nodemailer";

const transporter = nodemailer.createTransport({
  host: "smtp.tosend.com",
  port: 465,
  secure: true, // true for 465, false for 587
  auth: {
    user: "tosend",
    pass: process.env.TOSEND_API_KEY,
  },
});

await transporter.sendMail({
  from: "you@your-verified-domain.com",
  to: "dest@example.com",
  subject: "Hello from toSend",
  html: "<p>Sent over SMTP.</p>",
});

PHP (PHPMailer)

$mail = new PHPMailer\PHPMailer\PHPMailer(true);
$mail->isSMTP();
$mail->Host       = 'smtp.tosend.com';
$mail->SMTPAuth   = true;
$mail->Username   = 'tosend';
$mail->Password   = getenv('TOSEND_API_KEY');
$mail->SMTPSecure = PHPMailer\PHPMailer\PHPMailer::ENCRYPTION_SMTPS; // 465
$mail->Port       = 465;

$mail->setFrom('you@your-verified-domain.com');
$mail->addAddress('dest@example.com');
$mail->Subject = 'Hello from toSend';
$mail->Body    = 'Sent over SMTP.';
$mail->send();

Python (smtplib)

import os, smtplib
from email.message import EmailMessage

msg = EmailMessage()
msg["From"] = "you@your-verified-domain.com"
msg["To"] = "dest@example.com"
msg["Subject"] = "Hello from toSend"
msg.set_content("Sent over SMTP.")

with smtplib.SMTP_SSL("smtp.tosend.com", 465) as s:
    s.login("tosend", os.environ["TOSEND_API_KEY"])
    s.send_message(msg)

Supabase

In your Supabase project, go to Authentication → Emails → SMTP Settings, enable Custom SMTP, and use:

• Sender email: an address on your verified domain
• Host: smtp.tosend.com
• Port: 587
• Username: tosend
• Password: your toSend API key

Supabase routes its authentication emails (confirmations, password resets, magic links) through this connection.

Troubleshooting

• Authentication failed — check that the password is a valid API key and the key hasn’t been revoked.
• Message rejected / domain not allowed — the From domain must be verified in toSend.
• Connection times out — some hosts block outbound ports 465/587. Try the alternate ports 2465 (SSL/TLS) or 2587 (STARTTLS), or contact support.

Note

Every message sent over SMTP appears in your Email Logs with the same delivery, bounce, and complaint tracking as the API.