Why should you avoid using domains you don't control for email testing?

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
13Marketer 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?

February 2025 - 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.

September 2022 - Litmus
Marketer view

Marketer from Email Geeks shares that sending emails to `example.com` (or any domain you don't own) reminds him of when Microsoft had to step in and buy `corp.com` because people used the domain in Active Directory without thinking about what permissions they were delegating.

January 2023 - Email Geeks
Marketer view

Email marketer from Neil Patel explains that using domains you don't control can harm your sender reputation. If those domains are blacklisted or have poor engagement, it can negatively impact your deliverability.

October 2022 - Neil Patel
Marketer view

Marketer from Email Geeks advises against using anything you don't control, including Gmail, Hotmail, Yahoo, `example.com`, `yopmail.com` for testing.

March 2025 - Email Geeks
Marketer view

Email marketer from Reddit warns that using domains you don't control introduces potential security risks. If those domains are compromised, your test data could be exposed.

November 2022 - Reddit
Marketer view

Email marketer from Gmass explains that proper sender authentication (SPF, DKIM, DMARC) is crucial for deliverability. You need control of the domain to set up these records.

December 2023 - Gmass
Marketer view

Email marketer from StackOverflow mentions that using external domains pollutes your testing metrics. It's hard to get accurate results if you're not in full control of the environment.

February 2023 - StackOverflow
Marketer view

Email marketer from Sendinblue shares that using a dedicated IP address and domain allows you to build a positive sender reputation. This is impossible with domains you don't control.

March 2021 - Sendinblue
Marketer view

Email marketer from Campaign Monitor shares that setting up a separate test domain ensures that testing issues won't affect your main domain's reputation. Using domains you don't control defeats this purpose.

December 2021 - Campaign Monitor
Marketer view

Email marketer from SparkPost explains that using shared or free domains can lead to deliverability issues. It's better to use a dedicated domain that you manage.

March 2024 - SparkPost
Marketer view

Email marketer from Mailjet shares that using domains you don't control for testing can damage your brand reputation. Deliverability tests should use infrastructure you own and control.

September 2022 - Mailjet
Marketer view

Email marketer from Email On Acid responds that you lose control over crucial deliverability factors when using external domains. You can't manage SPF, DKIM, or DMARC records.

March 2021 - Email On Acid

What the experts say
1Expert opinion

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.

February 2023 - Word to the Wise

What the documentation says
4Technical 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.

March 2024 - 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.

September 2024 - Microsoft
Technical article

Documentation from MXToolbox explains that you need control over DNS records (SPF, DKIM, DMARC) for accurate deliverability testing. You can't modify DNS for domains you don't own.

May 2023 - MXToolbox
Technical article

Documentation from DMARC.org states that implementing DMARC on your sending domain protects it from spoofing and phishing. You need full control of the domain to implement DMARC effectively, something you can't do for domains you don't own.

December 2021 - DMARC.org