Send via SMTP

What Is an SMTP Relay?

An SMTP relay is a mail server that forwards email messages from a sender’s application to the recipient’s mail server. Instead of delivering email directly, the relay acts as an intermediary that handles authentication, queue management, and retry logic, improving deliverability for applications that send high volumes of transactional or marketing email.

If your application already sends email via SMTP, you can use RelayPost as a drop-in relay. No code changes needed — just update your SMTP settings.

SMTP server details

Setting	Value
Host	smtp.relaypost.dev
Port	587 (STARTTLS) or 465 (TLS)
Authentication	PLAIN or LOGIN
Username	Your SMTP credential username
Password	Your SMTP credential password
Encryption	TLS required

Create SMTP credentials

SMTP credentials are separate from API keys. Create them from the dashboard under Settings → SMTP Credentials:

1. Click Create Credential
2. Enter a username (or leave blank to auto-generate)
3. Add an optional description (e.g. “Production Rails App”)
4. Click Create and copy the password

Caution

The password is only shown once at creation time. Store it securely.

Configuration examples

Nodemailer

const nodemailer = require("nodemailer");

const transporter = nodemailer.createTransport({
host: "smtp.relaypost.dev",
port: 587,
secure: false,
auth: {
user: "smtp_a1b2c3d4",
pass: "your-smtp-password",
},
});

await transporter.sendMail({
from: "hello@yourapp.com",
to: "user@example.com",
subject: "Hello",
html: "<p>Sent via SMTP relay</p>",
});

Ruby on Rails

config/environments/production.rb

config.action_mailer.smtp_settings = {
  address: "smtp.relaypost.dev",
  port: 587,
  user_name: "smtp_a1b2c3d4",
  password: "your-smtp-password",
  authentication: :plain,
  enable_starttls_auto: true,
}

Django

settings.py

EMAIL_BACKEND = "django.core.mail.backends.smtp.EmailBackend"
EMAIL_HOST = "smtp.relaypost.dev"
EMAIL_PORT = 587
EMAIL_USE_TLS = True
EMAIL_HOST_USER = "smtp_a1b2c3d4"
EMAIL_HOST_PASSWORD = "your-smtp-password"

Laravel

.env

MAIL_MAILER=smtp
MAIL_HOST=smtp.relaypost.dev
MAIL_PORT=587
MAIL_USERNAME=smtp_a1b2c3d4
MAIL_PASSWORD=your-smtp-password
MAIL_ENCRYPTION=tls

SMTP vs API

	SMTP	API
Setup	Change SMTP config	Add HTTP calls
Features	Basic send	Full control (templates, scheduling, priority)
Speed	Connection overhead per session	Single HTTP request
Best for	Legacy apps, frameworks with built-in SMTP	New integrations, high-volume sending

Both methods deliver through the same infrastructure with the same deliverability. Choose based on what fits your stack.