SMTP relay

In the Supabase dashboard, open Authentication, then the SMTP settings under Emails, and turn on custom SMTP. Set the sender email to an address on your verified domain, the host to smtp.rasket.com, the port to 465, the username to rasket and the password to your key, then save. Sign-up confirmations, magic links and password resets now go through Rasket.

Supabase applies an hourly limit of its own to auth email. Raise it under Authentication → Rate Limits if your sign-ups need more. For a project run with the Supabase CLI, the same settings go in supabase/config.toml:

[auth.email.smtp]
enabled = true
host = "smtp.rasket.com"
port = 465
user = "rasket"
pass = "env(RASKET_API_KEY)"
admin_email = "auth@send.acme.example"
sender_name = "Acme"

secure: true is what port 465 needs; on 587 set secure: false and Nodemailer upgrades with STARTTLS. The two X-Rasket- headers are optional: see headers you can add.

import nodemailer from "nodemailer";

const transporter = nodemailer.createTransport({
  host: "smtp.rasket.com",
  port: 465,
  secure: true,
  auth: { user: "rasket", pass: process.env.RASKET_API_KEY },
});

await transporter.sendMail({
  from: "Acme <billing@send.acme.example>",
  to: "customer@example.com",
  subject: "Your receipt",
  text: "Thanks for your order.",
  headers: {
    "X-Rasket-Idempotency-Key": "receipt-1042",
    "X-Rasket-Tags": "category=receipt",
  },
});

WordPress sends through PHPMailer. Any SMTP plugin will do: give it the settings above, with SSL as the encryption. Without a plugin, add this to a small plugin of your own or to the theme's functions.php. The two filters matter, because WordPress otherwise sends from wordpress@ your site's domain, which is rarely the domain you verified.

add_action('phpmailer_init', function ($mailer) {
    $mailer->isSMTP();
    $mailer->Host = 'smtp.rasket.com';
    $mailer->Port = 465;
    $mailer->SMTPSecure = 'ssl';
    $mailer->SMTPAuth = true;
    $mailer->Username = 'rasket';
    $mailer->Password = getenv('RASKET_API_KEY');
});

add_filter('wp_mail_from', fn () => 'site@send.acme.example');
add_filter('wp_mail_from_name', fn () => 'Acme');

In .env. MAIL_SCHEME is read by Laravel 11 and later; earlier versions take MAIL_ENCRYPTION=ssl instead.

MAIL_MAILER=smtp
MAIL_SCHEME=smtps
MAIL_HOST=smtp.rasket.com
MAIL_PORT=465
MAIL_USERNAME=rasket
MAIL_PASSWORD="${RASKET_API_KEY}"
MAIL_FROM_ADDRESS="hello@send.acme.example"
MAIL_FROM_NAME="Acme"

In config/environments/production.rb. tls: true is implicit TLS, which is what port 465 speaks. On 587, drop it and set enable_starttls_auto: true instead.

config.action_mailer.delivery_method = :smtp
config.action_mailer.smtp_settings = {
  address: "smtp.rasket.com",
  port: 465,
  tls: true,
  authentication: :plain,
  user_name: "rasket",
  password: ENV.fetch("RASKET_API_KEY")
}

In settings.py, with os imported. EMAIL_USE_SSL is the setting for port 465. On 587 use EMAIL_USE_TLS instead; Django refuses both at once.

EMAIL_BACKEND = "django.core.mail.backends.smtp.EmailBackend"
EMAIL_HOST = "smtp.rasket.com"
EMAIL_PORT = 465
EMAIL_USE_SSL = True
EMAIL_HOST_USER = "rasket"
EMAIL_HOST_PASSWORD = os.environ["RASKET_API_KEY"]
DEFAULT_FROM_EMAIL = "Acme <hello@send.acme.example>"

If an app sends over SMTP today, the move is three settings: the host, the username and the password. Add and verify your domain in Rasket first, and keep the old provider until the domain reads verified, because a message from an unverified domain is refused with 550 5.7.1. A mailer that already sends an idempotency header for its old provider may keep sending it: one other provider's header is accepted verbatim, as is its SMTP username, and the comparison pages say which.