Why mailtester?

There are many email validation libraries out there. Here's why @mailtester/core stands out.

The Problem

Email validation seems simple, but it's not:

• Format validation isn't enough - test@fake-domain.xyz passes regex
• MX validation adds latency - every validation hits DNS
• SMTP validation is unreliable - servers block verification
• Disposable emails slip through - new services pop up daily
• Typos cause lost users - gmaill.com looks valid

Most libraries solve one problem. We solve them all.

Comparison

Feature	@mailtester/core	deep-email-validator	email-validator
RFC 5322 Regex	Full	Full	Basic
Typo Detection	Yes	Yes	No
Disposable Check	40K+ domains	Yes	No
MX Validation	Yes	Yes	No
SMTP Validation	Yes	Yes	No
Bulk Validation	Built-in	No	No
Rate Limiting	Built-in	No	No
TypeScript	Native	Basic types	Basic types
Scoring	0-100 score	No	No
Performance	3x faster	Slower	Fast
Bundle Size	25KB	50KB+	5KB
Maintained	Active	Limited	Active

Key Advantages

1. Performance

We're 3x faster than deep-email-validator:

• Single validation: < 150ms (without SMTP)
• Bulk 100 emails: < 5 seconds
• Optimized DNS lookups
• Efficient concurrency

2. TypeScript First

Built from the ground up with TypeScript 5.3+ strict mode:

// Full type safety and IntelliSense
import type { ValidationResult, Config } from '@mailtester/core';

const config: Config = {
  preset: 'strict',
  earlyExit: true
};

const result: ValidationResult = await validate('user@example.com', config);

3. Bulk Validation

Process thousands of emails efficiently:

const result = await validateBulk(emails, {
  concurrency: 20,
  rateLimit: {
    global: { requests: 100, window: 60 },
    perDomain: { requests: 5, window: 60 }
  },
  onProgress: (completed, total) => {
    console.log(`${completed}/${total}`);
  }
});

4. Smart Scoring

Get a reputation score (0-100) for each email:

const result = await validate('user@gmail.com');

console.log(result.score);  // 85
// Higher score = more trustworthy

5. Flexible Presets

Three presets for common use cases:

Preset	Use Case	Speed
strict	Maximum validation	~200ms
balanced	Good coverage, no SMTP	~100ms
permissive	Quick format check	~1ms

6. Modern Architecture

• Zero config - Works out of the box
• Tree-shakeable - Import only what you need
• ESM + CJS - Works everywhere
• Node.js 18+ - Modern runtime features

When to Use

Use @mailtester/core when you need:

• Comprehensive email validation
• Bulk email list cleaning
• User registration validation
• Marketing email verification
• TypeScript type safety
• High performance at scale

Consider alternatives when:

• You only need basic format validation → use validator.js
• You need browser-side validation → use regex only
• You're on Node.js < 18 → check compatibility

Getting Started

npm install @mailtester/core

import { validate } from '@mailtester/core';

const result = await validate('user@gmail.com');
console.log(result.valid);  // true
console.log(result.score);  // 85

Read the full documentation →