SMTP relay

import nodemailer from 'nodemailer';

const transport = nodemailer.createTransport({
  host: 'zapsmtp.xyz',
  port: 587, // STARTTLS
  auth: { user: process.env.ZAP_SMTP_USER, pass: process.env.ZAP_SMTP_PASSWORD },
});

await transport.sendMail({
  from: 'Acme <hello@acme.com>',
  to: 'delivered@simulator.zapsmtp.xyz',
  subject: 'Hello over SMTP',
  html: '<p>It works.</p>',
});

import os
import smtplib
from email.message import EmailMessage

msg = EmailMessage()
msg["From"] = "Acme <hello@acme.com>"
msg["To"] = "delivered@simulator.zapsmtp.xyz"
msg["Subject"] = "Hello over SMTP"
msg.set_content("It works.")

with smtplib.SMTP("zapsmtp.xyz", 587) as smtp:
    smtp.starttls()
    smtp.login(os.environ["ZAP_SMTP_USER"], os.environ["ZAP_SMTP_PASSWORD"])
    smtp.send_message(msg)

<?php
use PHPMailer\PHPMailer\PHPMailer;

$mail = new PHPMailer(true);
$mail->isSMTP();
$mail->Host = 'zapsmtp.xyz';
$mail->Port = 587;
$mail->SMTPSecure = PHPMailer::ENCRYPTION_STARTTLS;
$mail->SMTPAuth = true;
$mail->Username = getenv('ZAP_SMTP_USER');
$mail->Password = getenv('ZAP_SMTP_PASSWORD');

$mail->setFrom('hello@acme.com', 'Acme');
$mail->addAddress('delivered@simulator.zapsmtp.xyz');
$mail->Subject = 'Hello over SMTP';
$mail->Body = 'It works.';
$mail->send();

package main

import (
	"net/smtp"
	"os"
)

func main() {
	auth := smtp.PlainAuth("", os.Getenv("ZAP_SMTP_USER"), os.Getenv("ZAP_SMTP_PASSWORD"), "zapsmtp.xyz")
	msg := []byte("From: Acme <hello@acme.com>\r\n" +
		"To: delivered@simulator.zapsmtp.xyz\r\n" +
		"Subject: Hello over SMTP\r\n\r\nIt works.\r\n")
	// net/smtp upgrades to TLS with STARTTLS before authenticating
	err := smtp.SendMail("zapsmtp.xyz:587", auth, "hello@acme.com",
		[]string{"delivered@simulator.zapsmtp.xyz"}, msg)
	if err != nil {
		panic(err)
	}
}

require 'net/smtp'

msg = <<~MAIL
  From: Acme <hello@acme.com>
  To: delivered@simulator.zapsmtp.xyz
  Subject: Hello over SMTP

  It works.
MAIL

Net::SMTP.start('zapsmtp.xyz', 587, starttls: :always,
                user: ENV.fetch('ZAP_SMTP_USER'), secret: ENV.fetch('ZAP_SMTP_PASSWORD'),
                authtype: :plain) do |smtp|
  smtp.send_message(msg, 'hello@acme.com', 'delivered@simulator.zapsmtp.xyz')
end

MAIL_MAILER=smtp
MAIL_HOST=zapsmtp.xyz
MAIL_PORT=587
MAIL_ENCRYPTION=tls
MAIL_USERNAME=smtp_xxxxxxxxxxxx
MAIL_PASSWORD="your SMTP credential password"
MAIL_FROM_ADDRESS=hello@acme.com

EMAIL_BACKEND = "django.core.mail.backends.smtp.EmailBackend"
EMAIL_HOST = "zapsmtp.xyz"
EMAIL_PORT = 587
EMAIL_USE_TLS = True
EMAIL_HOST_USER = os.environ["ZAP_SMTP_USER"]
EMAIL_HOST_PASSWORD = os.environ["ZAP_SMTP_PASSWORD"]

swaks --server zapsmtp.xyz:587 --tls \
  --auth-user "$ZAP_SMTP_USER" --auth-password "$ZAP_SMTP_PASSWORD" \
  --from hello@acme.com --to delivered@simulator.zapsmtp.xyz \
  --header "Subject: Hello over SMTP" --body "It works."