Should I worry about test emails going to junk folders on irrelevant ISPs?

Summary

The prevailing opinion among experts, marketers, and documentation sources is that deliverability issues with test emails to irrelevant ISPs should not be a major concern. The primary focus should be on ensuring good deliverability to the ISPs used by your target audience and subscriber base. Overly broad testing, particularly sending test emails to irrelevant or spam trap addresses, can negatively affect your sender reputation. Furthermore, deliverability testing methodologies such as seed list testing have limitations and may not accurately reflect real-world user experiences.

Key findings

  • Focus on Relevant ISPs: Prioritize monitoring and ensuring good deliverability to ISPs used by your target audience.
  • Irrelevant ISPs Not Critical: Deliverability issues in irrelevant ISPs do not necessarily indicate a widespread problem.
  • Sender Reputation is Key: Avoid testing practices that negatively impact sender reputation (e.g., sending to spam traps).
  • Testing Limitations: Recognize that seed list tests and other methodologies have limitations and may not accurately reflect user experiences.
  • ISP Specific: Understand deliverability and sender reputation are often ISP-specific; problems with one provider may not affect others.

Key considerations

  • Targeted Testing: Concentrate testing efforts on ISPs relevant to your subscribers to gain meaningful insights.
  • Avoid Spam Traps: Be mindful of sending test emails to spam traps, as this can negatively impact your sender reputation.
  • Appropriate Methodologies: Choose testing methodologies that are most representative of real user experiences.
  • Monitor Key Metrics: Monitor key metrics like inbox placement at major ISPs where your subscribers are located.
  • Segmentation: Consider segmenting test lists by ISP for more accurate deliverability data. If you don't have subscribers in some segments you can ignore them.

What email marketers say
9Marketer opinions

The consensus is that deliverability issues with test emails to irrelevant ISPs should not be a primary concern. Email marketers should prioritize monitoring and ensuring good deliverability to the ISPs used by their target audience and subscriber base. Sending too many test emails to irrelevant or spam trap addresses can negatively impact sender reputation, so it's recommended to limit tests to representative inboxes or segment test lists by ISP.

Key opinions

  • Focus on relevant ISPs: Prioritize deliverability to ISPs used by your target audience (e.g., Gmail, Yahoo, Outlook for US subscribers).
  • Irrelevant ISPs not a concern: Junk folder placement in irrelevant ISPs typically doesn't indicate a widespread deliverability problem.
  • Testing limitations: Test results can vary, and issues at one ISP don't necessarily reflect overall deliverability.
  • Monitor inbox placement: Monitor inbox placement with tools for the key ISPs that host the majority of your subscribers’ inboxes.

Key considerations

  • Sender reputation: Avoid sending excessive test emails to irrelevant or spam trap addresses, as this can harm your sender reputation.
  • Test list segmentation: Consider segmenting your test list by ISP to get more accurate deliverability data for each provider.
  • Deliverability tools: Utilize deliverability testing tools to check inbox placement across various ISPs and mail clients to ensure you have proper deliverability.
  • Representative inboxes: Limit your testing to inboxes that are representative of your target audience and not spam traps.
Marketer view

Email marketer from EmailOctopus Blog explains that if the test emails are landing in the junk folders of ISPs that are not relevant to your target audience, it's generally not a cause for major concern. Focus on deliverability for ISPs where your subscribers are located.

April 2023 - EmailOctopus Blog
Marketer view

Email marketer from Mailjet Blog shares that you should prioritize monitoring deliverability to the ISPs your subscribers use. If the deliverability is good with those, then you shouldn't worry about other less used ones.

February 2022 - Mailjet Blog
Marketer view

Email marketer from Reddit shares that if you're primarily targeting US subscribers, focus on deliverability to Gmail, Yahoo, and Outlook. Ignore the results from Russian or German ISPs.

August 2021 - Reddit
Marketer view

Email marketer from an Email Marketing Forum suggests segmenting your test list by ISP to get more accurate deliverability data for each provider. Irrelevant ISPs can be ignored afterward.

May 2023 - Email Marketing Forum
Marketer view

Email marketer from GlockApps shares that if your test emails are hitting the junk folder in irrelevant ISPs, this doesn't mean that you have deliverability problems on the major email providers. They recommend prioritizing inbox placement monitoring on Gmail, Yahoo, Hotmail, AOL, and Outlook.

July 2022 - GlockApps Blog
Marketer view

Email marketer from HubSpot explains you should ensure your emails reach the inboxes of your subscribers, which might not include all ISPs. You may want to look at the deliverability for particular ISP's but only for the ones that matter.

February 2025 - HubSpot Blog
Marketer view

Email marketer from Litmus explains you should monitor inbox placement with tools for the key ISPs. Focus on the ISPs that host the majority of your subscribers’ inboxes to make sure you have proper deliverability.

January 2025 - Litmus Blog
Marketer view

Email marketer from Sendinblue Blog explains that test emails sent to a large number of spam traps or irrelevant ISPs can negatively affect your sender reputation. Limit tests to representative inboxes.

November 2023 - Sendinblue Blog
Marketer view

Email marketer from ZeroBounce shares that deliverability testing checks where emails land across various ISPs and mail clients. You may not need to take action based on negative tests from non-targetted providers.

September 2024 - ZeroBounce Blog

What the experts say
4Expert opinions

Experts generally agree that deliverability issues in test emails sent to irrelevant ISPs should not be a primary concern. The focus should be on ISPs that are relevant to your subscriber base. It's also important to recognize the limitations of seed list testing, as these tests may not accurately reflect the experience of real users at the same ISP. Furthermore, deliverability success can in theory vary between Gsuite and Gmail, but in practice, they usually tend to show the same results.

Key opinions

  • Focus on Relevant ISPs: Prioritize deliverability to ISPs where your actual subscribers are located.
  • Irrelevant ISPs less Important: Junk folder placement in irrelevant ISPs is generally not a cause for significant concern.
  • Seed List Limitations: Seed list tests may not accurately represent real-user experiences.
  • Gsuite vs Gmail deliverability: Deliverability results for Gsuite and Gmail tend to be similar in practice.

Key considerations

  • Targeted Approach: Base deliverability concerns on ISPs relevant to your subscriber demographics.
  • Test Method Awareness: Understand the limitations of different testing methods and how representative they are of real-world scenarios.
  • Monitor Reputation: Keep an eye on your sender reputation with major ISPs where your subscribers are located.
Expert view

Expert from Spamresource emphasizes focusing on the ISPs relevant to your subscriber base. Deliverability issues with less relevant ISPs should not be a major concern.

May 2024 - Spamresource
Expert view

Expert from Email Geeks explains that if the junk folders are from mailbox providers where you don't have subscribers, you generally don't need to be concerned.

March 2023 - Email Geeks
Expert view

Expert from Email Geeks shares that deliverability success can in theory vary between Gsuite and Gmail, but in practice, they usually tend to show the same results.

April 2024 - Email Geeks
Expert view

Expert from Word to the Wise explains that seed list tests have limitations, as some providers may treat seed accounts differently from real users. Furthermore, deliverability issues to certain test accounts don't necessarily reflect the experience of actual subscribers at the same ISP.

January 2025 - Word to the Wise

What the documentation says
4Technical articles

Email deliverability documentation highlights the complexity and ISP-specificity of spam filtering and sender reputation. Deliverability tests with irrelevant ISPs may not accurately reflect the experience of your actual subscribers, especially concerning services like Gmail or Microsoft Outlook. Each ISP operates independently, and sender reputation is also ISP-specific, meaning that problems at one ISP may not affect your reputation at another. Monitoring your sender reputation with Microsoft is only relevant if you have subscribers using their services.

Key findings

  • Complexity of Spam Filters: Gmail's spam filters consider numerous factors, so test emails may not accurately predict deliverability.
  • ISP-Specific Delivery: Mail server behavior and deliverability can vary widely between ISPs.
  • ISP-Specific Reputation: Sender reputation is ISP-specific, meaning deliverability issues at one ISP may not affect another.
  • Monitor Relevant Services: Monitor your sender reputation with services where your subscribers are present (e.g., Microsoft SNDS if using Outlook).

Key considerations

  • Targeted Testing: Focus deliverability testing on ISPs relevant to your target audience.
  • Understand ISP Variance: Recognize that deliverability varies across ISPs and that a problem with one may not be indicative of widespread issues.
  • Monitor Relevant Reputation: Track your sender reputation with the major ISPs where your subscribers have email accounts.
Technical article

Documentation from Google Postmaster Tools explains that Gmail's spam filters are complex and take into account numerous factors. Sending test emails to different ISPs may not accurately reflect how Gmail will treat your emails.

May 2021 - Google
Technical article

Documentation from SparkPost explains that your sender reputation is ISP-specific. Problems at one ISP may not affect your reputation at another.

January 2025 - SparkPost
Technical article

Documentation from RFC Editor about SMTP standards explain that mail server behavior can vary widely. Deliverability to one ISP doesn't guarantee deliverability to another.

May 2021 - RFC-Editor
Technical article

Documentation from Microsoft SNDS highlights monitoring your sender reputation with Microsoft. If you have no subscribers using Microsoft services then those are irrelevant.

May 2023 - Microsoft