Summary
Using domains you don't control for email testing poses significant risks. It can harm your sender and brand reputation, potentially leading to blacklisting and deliverability issues. These domains often lack proper authentication, may be compromised, or generate misleading testing metrics. Control over DNS records (SPF, DKIM, DMARC) is essential for accurate testing and security. Furthermore, unauthorized usage can cause integration problems with systems like Active Directory, and even trigger false spam flags by automated abuse systems. Therefore, experts recommend using dedicated, fully managed testing environments for reliable results and to avoid unintended consequences.
Key findings
- Reputation Damage: Using domains you don't control can harm your sender and brand reputation, potentially leading to blacklisting.
- Deliverability Issues: Lack of control over authentication (SPF, DKIM, DMARC) can cause deliverability problems.
- Security Risks: These domains can be compromised, exposing test data to security vulnerabilities.
- Inaccurate Metrics: Testing metrics become polluted, hindering the ability to accurately assess results.
- Integration Problems: Unauthorized usage can cause problems with systems like Active Directory.
- False Spam Flags: Automated abuse systems may misinterpret testing activities as spam.
Key considerations
- Dedicated Environment: Set up dedicated and fully managed testing environments with proper authentication.
- DNS Control: Ensure you have full control over DNS records (SPF, DKIM, DMARC) for accurate testing and security.
- Separate Testing: Keep your testing activities separate from your main sending infrastructure to protect its reputation.
- Reputation Monitoring: Monitor the reputation of your testing domains to address any issues promptly.
- Authorization: Ensure proper authorization when integrating domains with systems like Active Directory.
- Avoid Blacklisted Domains: Check to ensure the domain is not blacklisted
What email marketers say
13 marketer opinions
Using domains you don't control for email testing can severely compromise your deliverability, sender reputation, and brand image. These domains may have poor reputations, be blacklisted, or introduce security risks. Additionally, you lose control over critical authentication factors (SPF, DKIM, DMARC), pollute your testing metrics, and may encounter unpredictable behaviors or legal complications. Experts recommend using dedicated domains or sinkhole systems that you fully manage for accurate and safe testing.
Key opinions
- Reputation Damage: Domains you don't control may have poor reputations or be blacklisted, harming your sender reputation.
- Deliverability Issues: Shared or free domains can lead to deliverability problems, as you lack control over authentication.
- Security Risks: Using uncontrolled domains introduces potential security vulnerabilities and data exposure risks.
- Metric Pollution: External domains pollute testing metrics, making it difficult to obtain accurate results.
- Loss of Control: You lose control over SPF, DKIM, and DMARC records, essential for email authentication.
- Unpredictable Behavior: Domains like example.com may have unpredictable behavior or undergo unexpected changes, invalidating test results.
Key considerations
- Dedicated Infrastructure: Use dedicated domains or sinkhole systems that you fully manage for testing purposes.
- Authentication: Ensure proper sender authentication (SPF, DKIM, DMARC) on your testing domains.
- Separate Test Environment: Set up a separate test domain to isolate testing issues from your main domain's reputation.
- Monitor Reputation: Continuously monitor the reputation of your testing domains to address issues promptly.
- Avoid Disposable Services: Refrain from using disposable email services as they often have poor reputations and can skew test outcomes.
- Legal Compliance: Be mindful of legal and security implications when dealing with data sent to domains you don't own.
Marketer view
Marketer from Email Geeks explains more to the point, don't use a domain you don't control. You have no idea what the implications may be, or how that may change in the future. Is that more clear?
4 Jan 2022 - Email Geeks
Marketer view
Email marketer from Litmus cautions against using disposable email services for testing as they often have poor reputations. Their use can affect your deliverability testing results.
1 May 2025 - Litmus
What the experts say
1 expert opinions
Testing and list bombing using domains you don't control can send incorrect signals to automated abuse systems, potentially misinterpreting your activity as spam.
Key opinions
- Misinterpreted Signals: Using uncontrolled domains sends signals that automated abuse systems can misinterpret.
- False Spam Identification: Automated systems may incorrectly identify your testing as spam activity.
Key considerations
- Control Signals: Ensure your testing activities send correct signals to avoid misidentification as spam.
- Dedicated Infrastructure: Consider using a controlled testing environment to prevent misinterpretation.
Expert view
Expert from Word to the Wise explains that you should avoid testing and list bombing using domains you don't control, because that sends the wrong kind of signals. Even if you think you are doing it correctly, some automated abuse systems will misinterpret the signals and think you are a spammer.
5 Oct 2024 - Word to the Wise
What the documentation says
4 technical articles
Using domains you don't control for email testing can lead to unpredictable results due to their reserved status and potential changes in handling. It can also cause integration issues with systems like Active Directory, as demonstrated by the `corp.com` incident. Crucially, you lose the ability to manage essential DNS records like SPF, DKIM, and DMARC, preventing accurate deliverability testing and hindering protection against spoofing and phishing.
Key findings
- Unpredictable Results: Reserved domain names can lead to unpredictable results as their handling may change.
- Integration Issues: Unauthorized domain usage can cause problems integrating with systems like Active Directory.
- DNS Control Needed: Accurate deliverability testing requires control over DNS records (SPF, DKIM, DMARC).
- DMARC Implementation: Effective DMARC implementation, to protect against spoofing and phishing, requires domain control.
Key considerations
- Control DNS Records: Ensure you have full control over DNS records for proper testing and security.
- Avoid Reserved Domains: Avoid using reserved domain names for testing purposes.
- Proper Authorization: Ensure proper authorization when integrating domains with systems like Active Directory.
- DMARC Implementation: Implement DMARC on your sending domain to protect against spoofing and phishing.
Technical article
Documentation from RFC Editor states that `example.com`, `example.net`, `example.org` are reserved domain names. Using these for testing can lead to unpredictable results, as their handling might change.
6 Mar 2022 - RFC Editor
Technical article
Documentation from Microsoft explains that using domains without proper authorization can cause issues when integrating with Active Directory. Specifically referencing the `corp.com` incident, where unauthorized usage caused serious problems.
11 Jul 2022 - Microsoft
Are claims of 90 million email 'protestors' who do more than mark as spam accurate, and do ESPs sell data?
Can Mailosaur test email addresses negatively affect email deliverability?
How accurate are email spam testing tools and what are the alternatives?
How accurate are seed lists for email deliverability testing?
How can I accurately test and measure email deliverability and sender reputation?
Is it a good idea to verify email addresses by connecting to servers?
