// ts-zerosmtp.ts

/**

* TypeScript 7.x nodemailer 9.x - ZeroSMTP mx.msgwing.com:465 SSL/TLS

* Production-ready | Let's Encrypt | Branded types, satisfies operator

*/

import nodemailer from 'nodemailer';

import type { Transporter } from 'nodemailer';

// Branded types for type safety

type Username = string & { readonly __brand: 'Username' };

type Password = string & { readonly __brand: 'Password' };

type EmailAddress = string & { readonly __brand: 'EmailAddress' };

const createUsername = (u: string): Username => u as Username;

const createPassword = (p: string): Password => p as Password;

const createEmailAddress = (e: string): EmailAddress => e as EmailAddress;

interface ZeroSMTPConfig {

username: Username;

password: Password;

from: EmailAddress;

to: EmailAddress;

subject: string;

}

// NOTE: variable names are prefixed with ZEROSMTP_ to avoid colliding with

// reserved/OS-level variables (e.g. USERNAME is auto-set on Windows).

// Fail-fast: missing env vars exit with a clear error instead of silently

// using placeholder credentials that could leak into production.

const requiredVars = ['ZEROSMTP_USERNAME', 'ZEROSMTP_PASSWORD', 'ZEROSMTP_FROM', 'ZEROSMTP_TO'] as const;

const missing = requiredVars.filter((v) => !process.env[v]);

if (missing.length > 0) {

console.error(`ERROR: missing required environment variables: ${missing.join(', ')}`);

process.exit(1);

}

const config = {

username: createUsername(process.env.ZEROSMTP_USERNAME!),

password: createPassword(process.env.ZEROSMTP_PASSWORD!),

from: createEmailAddress(process.env.ZEROSMTP_FROM!),

to: createEmailAddress(process.env.ZEROSMTP_TO!),

subject: process.env.ZEROSMTP_SUBJECT || 'Test Email from ZeroSMTP',

} satisfies ZeroSMTPConfig;

async function sendEmailViaZeroSMTP(cfg: ZeroSMTPConfig): Promise<boolean> {

const transporter: Transporter = nodemailer.createTransport({

host: 'mx.msgwing.com',

port: 465,

secure: true,

auth: {

user: cfg.username,

pass: cfg.password,

},

tls: {

rejectUnauthorized: true,

minVersion: 'TLSv1.2',

},

});

const htmlBody: string = `<html><body><h1>Hello from ZeroSMTP!</h1><p>This is an HTML email sent via mx.msgwing.com:465</p></body></html>`;

const textBody: string = 'Hello from ZeroSMTP! This is plain text.';

try {

const info = await transporter.sendMail({

from: cfg.from,

to: cfg.to,

subject: cfg.subject,

text: textBody,

html: htmlBody,

});

console.log('Email sent:', info.messageId);

return true;

} catch (error) {

const err = error as Error & { code?: string };

if (err.code === 'EAUTH') {

console.error('Authentication failed:', err.message);

} else if (err.code === 'EHOSTUNREACH') {

console.error('Host unreachable:', err.message);

} else {

console.error('Email sending failed:', err.message);

}

return false;

}

}

process.exit(await sendEmailViaZeroSMTP(config) ? 0 : 1);