Spam Testing Domains: A Guide

TL;DR

Yes, there are domains available for cyber security companies to test spam filtering and detection systems. This guide covers free options (using dynamic DNS), paid registration of throwaway domains, and public testing services. It also details important considerations like reputation management.

1. Understanding the Need

Testing spam filters requires sending emails that *look* like spam without actually harming recipients. You need a domain you control to avoid blacklisting legitimate email infrastructure. Using your company’s main domain is strongly discouraged.

2. Free Options: Dynamic DNS (DDNS)

Dynamic DNS services provide a subdomain that updates with your IP address. This is free but comes with limitations regarding reputation and deliverability.

1. Choose a DDNS Provider: Services like No-IP, DynDNS (paid tiers offer better features), or DuckDNS are popular choices.
2. Create an Account & Hostname: Sign up for an account and create a hostname (e.g., mytestdomain.ddns.net).
3. Configure Your System: Point your email sending system to use the DDNS hostname as its SMTP server. You’ll likely need to configure DNS records, though most providers offer tools to help.
4. Limitations: These domains often have poor reputation scores and are easily blocked by spam filters. They’re best for initial testing or low-volume scenarios.

3. Paid Registration: Throwaway Domains

Registering a cheap domain specifically for testing is the most reliable free option, but requires some cost.

1. Choose a Registrar: Namecheap, GoDaddy, or Porkbun are good options. Look for domains costing around £5-£10 per year.
2. Register a Domain: Choose a name that isn’t associated with your company and doesn’t resemble legitimate brands. Avoid common words.
3. Configure DNS Records: Set up MX records to point to your email server or use a mail relay service (see section 4).
4. Warm-up the Domain: Gradually increase sending volume over several days/weeks to build reputation. Start with very low volumes and monitor deliverability.

4. Mail Relay Services

Using a mail relay service simplifies email sending and can improve deliverability, even with throwaway domains.

• Popular Options: SendGrid, Mailjet, Postmark are common choices (often have free tiers for low volume).
• Integration: Integrate the relay service into your testing system. They provide APIs or SMTP settings to use.
• Benefits: Handle bounce processing, feedback loops, and reputation management more effectively than setting up your own server.

5. Public Spam Testing Services

Some services offer pre-configured domains for testing spam filters.

• Spamhaus Blocklist Checker: While not a domain provider, it allows you to check if your test domain is blacklisted. https://check.spamhaus.org
• Mail-Tester.com: Provides a score for your email and identifies issues that might cause spam filtering. Requires an email address on the domain you are testing.

6. Reputation Management – Crucial!

Regardless of the method, monitor your domain’s reputation.

• Blacklist Checks: Regularly check against major blacklists (Spamhaus, Barracuda, etc.).
• Feedback Loops: If using a relay service, ensure feedback loops are configured to handle bounce and complaint data.
• Sender Score: Monitor your Sender Score (Return Path) to assess deliverability.

7. Important Considerations

• Terms of Service: Always review the terms of service for any DDNS provider or mail relay service before using them for spam testing. Some prohibit this use case.
• Avoid Harm: Never send unsolicited emails to real users. Testing should be done in a controlled environment with willing participants or dedicated test accounts.
• Data Privacy: Be mindful of data privacy regulations (GDPR, etc.) when handling email addresses used for testing.