Sending email from your app

import nodemailer from "nodemailer";

const transport = nodemailer.createTransport({
  host: "smtp.testlie.com",
  port: 587,
  secure: false, // true only for port 465; STARTTLS is used automatically when offered
  auth: { user: process.env.SMTP_USER, pass: process.env.SMTP_PASS },
});

await transport.sendMail({
  from: "app@example.com",
  to: "new-user@example.com",
  subject: "Welcome aboard",
  html: "<h1>Hi!</h1><a href='https://app.example.com/verify'>Verify</a>",
});

import os, smtplib
from email.message import EmailMessage

msg = EmailMessage()
msg["From"] = "app@example.com"
msg["To"] = "new-user@example.com"
msg["Subject"] = "Welcome aboard"
msg.set_content("Hi! Verify your account: https://app.example.com/verify")
msg.add_alternative("<h1>Hi!</h1><a href='https://app.example.com/verify'>Verify</a>", subtype="html")

with smtplib.SMTP("smtp.testlie.com", 587) as smtp:
    smtp.starttls()  # omit if the server has no TLS certificate
    smtp.login(os.environ["SMTP_USER"], os.environ["SMTP_PASS"])
    smtp.send_message(msg)

# settings/staging.py
EMAIL_BACKEND = "django.core.mail.backends.smtp.EmailBackend"
EMAIL_HOST = "smtp.testlie.com"
EMAIL_PORT = 587
EMAIL_HOST_USER = os.environ["SMTP_USER"]
EMAIL_HOST_PASSWORD = os.environ["SMTP_PASS"]
EMAIL_USE_TLS = True   # STARTTLS; set False if the server has no certificate
# For port 465 use EMAIL_USE_SSL = True instead (and EMAIL_USE_TLS = False).

# config/environments/staging.rb
config.action_mailer.delivery_method = :smtp
config.action_mailer.smtp_settings = {
  address: "smtp.testlie.com",
  port: 587,
  user_name: ENV["SMTP_USER"],
  password: ENV["SMTP_PASS"],
  authentication: :plain,
  enable_starttls_auto: true
}
config.action_mailer.default_url_options = { host: "staging.example.com" }

# .env
MAIL_MAILER=smtp
MAIL_HOST=smtp.testlie.com
MAIL_PORT=587
MAIL_USERNAME=your-inbox-username
MAIL_PASSWORD=your-inbox-password
MAIL_ENCRYPTION=tls
MAIL_FROM_ADDRESS=app@example.com

# application-staging.properties
spring.mail.host=smtp.testlie.com
spring.mail.port=587
spring.mail.username=${SMTP_USER}
spring.mail.password=${SMTP_PASS}
spring.mail.properties.mail.smtp.auth=true
spring.mail.properties.mail.smtp.starttls.enable=true

@Autowired JavaMailSender mailSender;

var message = new SimpleMailMessage();
message.setFrom("app@example.com");
message.setTo("new-user@example.com");
message.setSubject("Welcome aboard");
message.setText("Hi! Verify your account: https://app.example.com/verify");
mailSender.send(message);

// dotnet add package MailKit
using MailKit.Net.Smtp;
using MailKit.Security;
using MimeKit;

var message = new MimeMessage();
message.From.Add(MailboxAddress.Parse("app@example.com"));
message.To.Add(MailboxAddress.Parse("new-user@example.com"));
message.Subject = "Welcome aboard";
message.Body = new TextPart("html") { Text = "<h1>Hi!</h1>" };

using var client = new SmtpClient();
await client.ConnectAsync("smtp.testlie.com", 587, SecureSocketOptions.StartTlsWhenAvailable);
await client.AuthenticateAsync(Environment.GetEnvironmentVariable("SMTP_USER"), Environment.GetEnvironmentVariable("SMTP_PASS"));
await client.SendAsync(message);
await client.DisconnectAsync(true);

package main

import (
	"net/smtp"
	"os"
)

func main() {
	// SendMail upgrades with STARTTLS when the server offers it. PlainAuth refuses to send a
	// password over an unencrypted connection, except to localhost.
	auth := smtp.PlainAuth("", os.Getenv("SMTP_USER"), os.Getenv("SMTP_PASS"), "smtp.testlie.com")
	msg := []byte("From: app@example.com\r\n" +
		"To: new-user@example.com\r\n" +
		"Subject: Welcome aboard\r\n\r\n" +
		"Hi! Verify your account: https://app.example.com/verify\r\n")
	err := smtp.SendMail("smtp.testlie.com:587", auth, "app@example.com", []string{"new-user@example.com"}, msg)
	if err != nil {
		panic(err)
	}
}