EmailDomainValidator 2.0.0.62

EmailDomainValidator

A lightweight, free .NET library for validating email addresses — checking format, detecting disposable domains, and verifying real MX records.

Key Features

• Email Format Validation — regex-based format check (user@domain.com)
• Disposable Email Detection — blocks known throwaway domains (5,400+ entries, embedded at build time)
• Real MX Record Verification — uses actual DNS MX queries via DnsClient.NET, not just A-record resolution
• Rich Validation Results — ValidationResult tells you why an email failed (InvalidFormat, DisposableDomain, NoMxRecords)
• Dependency Injection Support — register via services.AddEmailDomainValidator() or use the static API
• Configurable Options — tune cache TTL and blocklist update URL via EmailValidatorOptions
• Blocklist Update Mechanism — refresh the in-memory blocklist at runtime from any URL, no restart required
• Async Support — every method has an async counterpart
• MX Result Caching — DNS lookups are cached (default: 1 hour) to avoid redundant queries

Installation

dotnet add package EmailDomainValidator

Quick Start

Static API

using EmailDomainValidator;

// Simple bool check
bool isValid = EmailValidator.ValidateEmail("user@example.com");

// Async
bool isValid = await EmailValidator.ValidateEmailAsync("user@example.com");

// Detailed result — know exactly why validation failed
ValidationResult result = EmailValidator.ValidateEmailWithResult("user@mailinator.com");
// result.IsValid        -> false
// result.FailureReason  -> ValidationFailureReason.DisposableDomain

// Implicit bool conversion
if (!result) Console.WriteLine($"Rejected: {result.FailureReason}");

Dependency Injection (ASP.NET Core / Generic Host)

// Program.cs
builder.Services.AddEmailDomainValidator();

// Or with custom options
builder.Services.AddEmailDomainValidator(options =>
{
    options.CacheTtl = TimeSpan.FromMinutes(30);
});

// In a controller, service, etc.
public class RegistrationService(IEmailDomainValidator validator)
{
    public async Task RegisterAsync(string email)
    {
        var result = await validator.ValidateEmailWithResultAsync(email);
        if (!result)
            throw new ArgumentException($"Invalid email: {result.FailureReason}");
        // ...
    }
}

API Reference

EmailValidator (static class) / IEmailDomainValidator (interface)

ValidationResult

result.IsValid        // bool
result.FailureReason  // ValidationFailureReason enum
(bool)result          // implicit conversion
result.ToString()     // "Valid" or "Invalid: DisposableDomain"

ValidationFailureReason values: None, InvalidFormat, DisposableDomain, NoMxRecords

EmailValidatorOptions

new EmailValidatorOptions
{
    CacheTtl = TimeSpan.FromHours(1),   // how long MX results are cached
    BlocklistUpdateUrl = null            // optional URL for runtime blocklist refresh
}

Disposable Email Blocklist

The embedded blocklist ships with 5,400+ known disposable domains and is sourced from the community-maintained disposable-email-domains project.

Since new disposable providers appear regularly, the library provides a runtime update mechanism so your application can refresh the list without a redeployment:

// Refresh at startup or on a schedule
await EmailValidator.UpdateBlocklistAsync(
    "https://raw.githubusercontent.com/disposable-email-domains/disposable-email-domains/master/disposable_email_blocklist.conf"
);

The new list is swapped in atomically — no downtime, no restart.

Dependencies

Use Cases

• User Registration — block fake/throwaway accounts at sign-up
• Newsletter Subscriptions — keep mailing lists clean
• E-commerce — reduce fraud and improve delivery rates
• Lead Generation — validate form submissions before they hit your CRM
• Data Cleaning — validate existing email datasets in bulk

Contributing

Contributions are welcome. Please fork the repository, make your changes on a feature branch, and open a pull request. For significant changes, open an issue first.

License

MIT — see LICENSE for details.

Links

• NuGet Package
• GitHub Repository
• Upstream Blocklist