email-domain-check

A comprehensive email domain validation library. Supports DNS, MX, SMTP, DKIM, DMARC, and MTA-STS.

Features

• MX record validation
• SMTP server connection testing
• DKIM record lookup
• DMARC policy validation
• MTA-STS support (RFC 8461)
• IPv4/IPv6 support
• Local IP blocking
• DNS failover resolvers
• Punycode/IDN support
• TypeScript support

Installation

npm install email-domain-check
# or
pnpm add email-domain-check
# or
yarn add email-domain-check
# or
bun add email-domain-check

Usage (ESM / TypeScript)

import { Address, DomainChecker } from 'email-domain-check';

const checker = new DomainChecker();

// Check if domain has MX records
const hasMx = await checker.hasMxRecord('[email protected]');
console.log('Has MX:', hasMx);

// Get MX records with priority
const mxRecords = await checker.getMxRecord({
	target: 'gmail.com', // string, URL or Address
	useCache: false,
	preferDomainNS: false, // use authoritative ns `ns1.google.com`
});
console.log('MX Records:', mxRecords);
// [{ exchange: 'gmail-smtp-in.l.google.com', priority: 5 }]

// use url, domain or email
const url = new URL('https://gmail.com');
const addr_01 = Address.loadFromTarget(url);
const addr_02 = Address.loadFromTarget('gmail.com');
const addr_03 = Address.loadFromTarget('[email protected]');
const addr_04 = new Address('[email protected]'); // email or domain

console.log('Has MX 01:', await checker.hasMxRecord(addr_01));
console.log('Has MX 02:', await checker.hasMxRecord(addr_02));
console.log('Has MX 03:', await checker.hasMxRecord(addr_03));
console.log('Has MX 04:', await checker.hasMxRecord(addr_04));
// or direct use
console.log('Has MX 05:', await checker.hasMxRecord(new URL('https://gmail.com')));
console.log('Has MX 06:', await checker.hasMxRecord('gmail.com'));
console.log('Has MX 07:', await checker.hasMxRecord('[email protected]'));
console.log('Has MX 08:', await checker.hasMxRecord('[email protected]'));

Usage (CommonJS)

const { DomainChecker } = require('email-domain-check');

async function run() {
	const checker = new DomainChecker();

	// Check if domain has MX records
	const hasMx = await checker.hasMxRecord('[email protected]');
	console.log('Has MX:', hasMx);

	// Get MX records with priority
	const mxRecords = await checker.getMxRecord({
		target: 'gmail.com', // string, URL or Address
		useCache: false,
		preferDomainNS: false, // use authoritative ns `ns1.google.com`
	});
	console.log('MX Records:', mxRecords);
	// [{ exchange: 'gmail-smtp-in.l.google.com', priority: 5 }]
}

run();

Advance Usage

Get Records

import { DomainChecker } from 'email-domain-check';

const checker = new DomainChecker();

// Get SPF record
const spf = await checker.getSpfRecord({
	target: '[email protected]',
	dkimSelector: 'k1',
});
console.log('SPF:', spf);

// Get DKIM record
const dkim = await checker.getDkimRecord({
	target: '[email protected]',
	dkimSelector: 'k1',
});
console.log('DKIM:', dkim);

// Get DMARC record
const dmarc = await checker.getDmarcRecord({
	target: 'gmail.com',
});
console.log('DMARC:', dmarc);

// Get MTA-STS record
const sts = await checker.getStsRecord({
	target: '[email protected]',
});
console.log('MTA-STS:', sts);

// Get custom records
const customRecords = await checker.getCustomRecords({
	target: '[email protected]',
});
console.log('Custom Records:', customRecords);

// Get custom kv record
const kvRecord = await checker.getCustomKVRecord(
	{
		target: '[email protected]',
	},
	'yahoo-verification-key',
);
console.log('KV Record:', kvRecord);

// Get custom kv record
const allKVRecord = await checker.getAllKVRecords({
	target: '[email protected]',
});
console.log('All KV Records:', allKVRecord);

Get Authoritative Name Servers

import { DomainChecker } from "email-domain-check";
const checker = new DomainChecker();

// Get name servers
const nameServers = await checker.getNameServers("gmail.com");
console.log("Name Servers:", nameServers);

Get SMTP Connection

import { DomainChecker } from "email-domain-check";

const checker = new DomainChecker();
// Test or Get SMTP connection for mail sending
const socket = await checker.getSmtpConnection("[email protected]");
if (socket) {
  console.log("SMTP connection successful");
  socket.end();
}

MTA-STS Policy

import { getMtaStsPolicy, isMxAllowed } from "email-domain-check";

const policy = await getMtaStsPolicy("gmail.com");
if (policy) {
  console.log("MTA-STS Policy:", policy);
  // { version: 'STSv1', mode: 'enforce', mx: ['*.google.com'], max_age: 86400 }
  
  const allowed = isMxAllowed("alt1.gmail-smtp-in.l.google.com", policy);
  console.log("MX Allowed:", allowed);
}

Address Parsing and Validation

import {Address } from "email-domain-check";
// Address parsing and validation
const addr = Address.loadFromTarget("[email protected]");
console.log("Hostname:", addr.hostname); // example.com
console.log("User:", addr.user); // user
console.log("Is IP:", addr.isIP); // false
console.log("Is Local:", addr.isLocal); // false
console.log("Has Punycode:", addr.hasPunycode); // false

// Parse from URL
const url = new URL("https://example.com/path");
const urlAddr = Address.loadFromTarget(url);
console.log("From URL:", urlAddr.hostname); // example.com

// IP address validation
const Addr_01 = new Address("192.168.1.1");
console.log("Is Local IP:", Addr_01.isLocal); // true

const Addr_02 = new Address("8.8.8.8");
console.log("Is Local IP:", Addr_02.isLocal); // false

API

DomainChecker Class

Constructor Options

interface DomainCheckerOptions {
  server?: string[];            // Custom DNS servers
  dkimSelector?: string;        // Default: 'default'
  useCache?: boolean;           // Enable DNS caching
  cacheTTL?: number;            // Cache TTL in ms
  smtpTimeout?: number;         // Default: 10000
  dnsTimeout?: number;          // Default: 5000
  httpTimeout?: number;         // Default: 8000
  socketIdleTimeout?: number;   // RFC 5321 socket idle timeout
  useDomainNS?: boolean;        // Query domain's authoritative nameservers (Default: false)
  useMtaSts?: boolean;          // Enable MTA-STS related lookups (Default: false)
  ignoreIPv6?: boolean;         // Ignore IPv6 addresses
  tries?: number;               // Default: 3
  failoverServers?: string[][]; // Default: [['1.1.1.1','1.0.0.1'], ['8.8.8.8','8.8.4.4']]
  blockLocalIPs?: boolean;      // Block local/private IPs (Default: false)
  deliveryPort?: number;        // Default: 25
}

Methods

• hasMxRecord(target: Target): Promise<boolean> - Check if domain has MX records
• getMxRecord(options: ResolveOptions): Promise<MxRecord[]> - Get MX records
• getSmtpConnection(target: Target): Promise<Socket | null> - Test SMTP connection
• getTxtRecord(options: ResolveOptions): Promise<TXTResult | null> - Get all TXT records parsed
• getSpfRecord(options: ResolveOptions): Promise<SPF1Record | null> - Get SPF record
• getDkimRecord(options: ResolveOptions): Promise<DKIM1Record | null> - Get DKIM record
• getDmarcRecord(options: ResolveOptions): Promise<DMARC1Record | null> - Get DMARC record
• getStsRecord(options: ResolveOptions): Promise<STSv1Record | null> - Get MTA-STS record
• getCustomRecords(options: ResolveOptions): Promise<CustomRecord[] | null> - Get custom TXT records
• getCustomKVRecord(options: ResolveOptions, key: string): Promise<CustomKVRecord | null> - Get specific key-value record
• getAllKVRecords(options: ResolveOptions): Promise<CustomKVRecord[] | null> - Get all key-value records
• getNameServers(target: Target): Promise<string[]> - Get authoritative name servers

Address Class

Constructor

• new Address(mailOrHost: string) - Create new Address instance

import {Address } from "email-domain-check";
const addr_01 = new Address('[email protected]'); // string email or domain
const addr_02 = new Address('gmail.com'); 

Static Constructor Method

• Address.loadFromTarget(target: string | URL | Address): Address - Parse email/domain/URL

Properties

• source: string - Original input
• hostname: string - Domain name or IP
• user?: string - Email local part (if email)
• ipKind: IPKind - IP type (None, IPv4, IPv6)
• isIP: boolean - Is an IP address
• isLocal: boolean - Is local/private IP
• hasPunycode: boolean - Contains punycode