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Why are AOL and Yahoo flagging emails as spam?

12 Marketer opinions4 Expert opinions5 Technical articles1 Resource

Summary

AOL and Yahoo flag emails as spam due to a combination of factors related to sender reputation, user engagement, email authentication, content, and list hygiene. A negative sender reputation, often stemming from user behavior indicating emails are unwanted, being blacklisted, or sending to spam traps, is a primary driver. Lack of user engagement and sending unsolicited emails also contribute significantly. Failing to properly authenticate emails with SPF, DKIM, and DMARC makes it difficult for ISPs to verify legitimacy, increasing the likelihood of spam flagging. Suspicious content, poor formatting, spam trigger words, and misleading subject lines can also trigger spam filters. Maintaining a clean email list and gradually increasing email volume with new IPs are essential for improving deliverability. Ultimately, sending relevant, personalized emails to engaged subscribers while adhering to email best practices is crucial to avoid spam flagging by AOL and Yahoo.

Key findings

  • Sender Reputation is Paramount: A strong, positive sender reputation is the most critical factor. This is influenced by IP reputation, domain reputation, spam complaints, and blocklist status.
  • User Engagement Matters: User interaction (opens, clicks, deletions, spam reports) signals to ISPs whether users want the emails. Low engagement rates significantly increase spam flagging.
  • Email Authentication is Essential: Proper implementation and maintenance of SPF, DKIM, and DMARC records are crucial for verifying sender identity and preventing domain spoofing. Authentication helps ISPs trust emails.
  • Content Quality Influences Deliverability: Spam trigger words, poor formatting, excessive use of images without alt text, and misleading subject lines can trigger spam filters, regardless of sender reputation.
  • List Hygiene is Non-Negotiable: Regularly cleaning email lists to remove inactive or invalid addresses reduces bounce rates, improves sender reputation, and minimizes the risk of being flagged as spam.

Key considerations

  • Actively Manage Your Reputation: Use tools like Google Postmaster Tools and Sender Score to monitor sender reputation. Proactively address any issues and work to improve your reputation score.
  • Segment and Personalize Your Emails: Tailor email content to specific segments of your audience to increase engagement. Personalize emails to make them more relevant and desirable to recipients.
  • Prioritize Email Authentication: Ensure that SPF, DKIM, and DMARC records are correctly configured and regularly updated. Implement a DMARC policy to instruct receiving servers on how to handle authentication failures.
  • Optimize Email Content and Design: Avoid spam trigger words, use clear and concise subject lines, ensure emails are well-formatted with a healthy text-to-image ratio, and use alt text for images.
  • Practice Rigorous List Hygiene: Implement a process for regularly cleaning your email list, removing inactive subscribers, and validating email addresses to maintain a healthy list.
  • Get Explicit Permission: Always get explicit permission before sending someone emails and honor unsubscribe requests promptly.
  • Monitor Sending Volume: Gradually increase sending volume, especially when using a new IP address or domain, to establish a positive sender reputation.

What email marketers say
12Marketer opinions

Emails are flagged as spam by AOL and Yahoo for a variety of reasons, including poor sender reputation, sending to unengaged subscribers, using spam trigger words, high spam complaint rates, lacking proper authentication (SPF, DKIM, DMARC), suspicious content, poor email formatting, misleading subject lines, and a lack of unsubscribe options. User engagement is also a significant factor, as ISPs monitor how users interact with emails. Maintaining a clean email list, gradually increasing email volume with new IPs, personalizing emails, and sending relevant content are crucial for improving deliverability and avoiding spam filters. Reputation data influences spam filtering, and being added to a blacklist can hinder email delivery. Emails that are well-coded, have a healthy text-to-image ratio, and use alt text for images are also less likely to be flagged as spam.

Key opinions

  • Sender Reputation: Poor sender reputation is a primary driver for spam flagging. This encompasses factors like domain reputation, IP address reputation, and historical spam complaints.
  • User Engagement: ISPs analyze user engagement with emails (opens, clicks, etc.) to determine if emails are wanted. Low engagement leads to increased spam flagging.
  • Authentication: Lack of proper email authentication (SPF, DKIM, DMARC) makes it difficult for ISPs to verify the legitimacy of emails, leading to higher spam filtering rates.
  • Content & Formatting: Spam trigger words, excessive use of exclamation points or ALL CAPS, poor HTML coding, and high image-to-text ratios contribute to spam flagging.
  • List Hygiene: Maintaining a clean email list by removing inactive or invalid addresses reduces bounce rates and improves sender reputation.

Key considerations

  • Monitor Reputation: Actively monitor your sender reputation using tools like Google Postmaster Tools and take steps to improve it if needed.
  • Improve Engagement: Focus on sending relevant, personalized emails to encourage user engagement. Segment your list to send targeted content.
  • Implement Authentication: Set up SPF, DKIM, and DMARC records to authenticate your emails and prevent spoofing.
  • Review Content: Avoid using spam trigger words, excessive punctuation, and ensure emails are well-formatted with a healthy text-to-image ratio.
  • Clean Email List: Regularly clean your email list by removing inactive or invalid addresses to improve deliverability and sender reputation.
  • IP Warmup: Gradually increase sending volume on a new IP address to establish a positive reputation with ISPs.
  • Permission: Always get permission to send subscribers emails. Send relevant content to people who want to receive it.
Marketer view

Marketer from Email Geeks reports that Yahoo and AOL came back for them naturally.

December 2021 - Email Geeks
Marketer view

Email marketer from Quora shares that maintaining a clean email list by removing inactive or invalid email addresses reduces bounce rates and helps improve sender reputation, thereby decreasing the chances of being marked as spam.

March 2023 - Quora
Marketer view

Email marketer from Constant Contact Blog responds that to avoid the spam folder, you should get permission to email subscribers, authenticate your email, clean your email list regularly, and test your emails before sending.

June 2021 - Constant Contact Blog
Marketer view

Email marketer from Reddit shares that a poor domain reputation can significantly impact deliverability, with ISPs often blocking or filtering emails from domains with a history of sending spam.

May 2023 - Reddit
Marketer view

Email marketer from Sendinblue Blog shares that spam filters look for things like suspicious words, poor formatting, misleading subject lines, and a lack of unsubscribe options.

December 2024 - Sendinblue Blog
Marketer view

Marketer from Email Geeks shares that they are having the same issue as the original poster, for about the same amount of time and someone contacted Yahoo which said they are being marked as spam more and wonders if they made some changes.

June 2022 - Email Geeks
Marketer view

Email marketer from StackOverflow explains that using excessive exclamation points, ALL CAPS, or certain trigger words (like 'free' or 'guarantee') can increase the likelihood of emails being flagged as spam.

July 2022 - StackOverflow
Marketer view

Email marketer from MailerLite Blog explains that emails might be flagged as spam because of poor sender reputation, sending to unengaged subscribers, using spam trigger words, having a high spam complaint rate, or lacking proper authentication.

August 2024 - MailerLite Blog
Marketer view

Email marketer from GMass Blog explains that gradually increasing email volume when using a new IP address helps establish a positive sender reputation and avoids being immediately flagged as a spammer.

August 2021 - GMass Blog
Marketer view

Email marketer from Mailjet responds that personalizing emails with recipient names and relevant content can increase engagement and reduce the likelihood of being marked as spam.

November 2024 - Mailjet
Marketer view

Email marketer from Hubspot answers that sending relevant emails to people is one of the most important things you can do to avoid spam flagging. Make sure people want to receive your emails.

August 2023 - HubSpot
Marketer view

Email marketer from Litmus Blog responds that poorly coded emails, using excessive images without alt text, and having a low text-to-image ratio can trigger spam filters.

August 2024 - Litmus Blog

What the experts say
4Expert opinions

AOL and Yahoo flag emails as spam primarily due to negative reputation factors, which can stem from user behavior indicating the emails are unwanted, such as not engaging with the content. Other reasons include being blacklisted by ESPs or companies, sending spam-like content, failing to authenticate emails properly, and sending to spam traps. The consensus is that user engagement and sender reputation are critical determinants in whether emails are marked as spam.

Key opinions

  • User Reaction: User behavior and engagement (or lack thereof) significantly influence whether ISPs flag emails as spam. Unwanted emails, as perceived by users, contribute to deliverability issues.
  • Reputation: Negative reputation factors, based on data collected by ISPs, lead to filtering and blocking of emails. This reputation is a key driver behind AOL and Yahoo's spam flagging.
  • Blacklisting: Being added to a blacklist by ESPs or other organizations results in blocked emails, as these lists are used to filter out potentially harmful or unwanted senders.
  • Content & Authentication: Spam-like content and failure to authenticate emails (SPF, DKIM, DMARC) increase the likelihood of emails being flagged as spam by AOL and Yahoo.

Key considerations

  • Improve Engagement: Focus on sending emails that users want to receive and engage with. This involves creating relevant content, segmenting audiences, and avoiding tactics that might be perceived as spammy.
  • Monitor Reputation: Regularly check sender reputation using tools like Google Postmaster Tools and take steps to address any negative feedback or issues.
  • Avoid Blacklists: Ensure email practices align with best practices to avoid being added to blacklists. Monitor blacklists and take corrective actions if listed.
  • Implement Authentication: Ensure that SPF, DKIM, and DMARC records are correctly configured to authenticate emails and prevent spoofing.
  • Review Content: Carefully review email content to avoid using spam trigger words, misleading subject lines, and other tactics that could trigger spam filters.
Expert view

Expert from Spamresource shares that emails get blocked because ESPs or companies added you to a blacklist, your messages contain spam-like content, you aren't authenticating your emails, or you send spam traps emails.

September 2021 - Spamresource
Expert view

Expert from Spamresource explains that reputation data is used to filter and sometimes block mail. If Yahoo and AOL are flagging mail, this is based on some negative reputation factor.

August 2022 - Spamresource
Expert view

Expert from Email Geeks explains that the root of most delivery issues is: users are reacting in ways that tell the ISP the mail is unwanted.

January 2023 - Email Geeks
Expert view

Expert from Word to the Wise explains that one of the main reasons for spam flagging is lack of user engagement, ISPs pay attention to what users do with your emails to determine what is spam.

December 2021 - Word to the Wise

What the documentation says
5Technical articles

AOL and Yahoo flag emails as spam due to several technical and policy-related reasons, as detailed in official documentation. These include sending unsolicited emails, containing suspicious content, lacking proper email authentication (SPF, DKIM, DMARC), having a poor sender reputation, and being listed on a major blocklist due to spam activities. Implementing a DMARC policy to handle authentication failures, providing clear unsubscribe options, and actively managing sender reputation are crucial to avoid spam flagging.

Key findings

  • Authentication: Proper SPF, DKIM, and DMARC records are essential for ISPs to verify the legitimacy of emails and reduce the risk of spam flagging. DMARC policies instruct receiving servers on how to handle authentication failures, preventing domain spoofing.
  • Sender Reputation: A poor sender reputation, often stemming from spam complaints or being listed on blocklists, leads to filtering or blocking of emails by ISPs like AOL and Yahoo.
  • Unsolicited Content: Sending unsolicited emails, which are often associated with spam, contributes to higher spam flagging rates.
  • Bulk Sending Policies: Bulk senders are responsible for ensuring they have clear unsubscribe options and managing their sender reputation to avoid being flagged as spam.
  • Blocklisting: Inclusion on a major blocklist, like those maintained by Spamhaus, directly results in ISPs filtering or blocking emails.

Key considerations

  • Implement Authentication: Configure SPF, DKIM, and DMARC records correctly to authenticate emails and prevent domain spoofing. Regularly review and update these records.
  • Manage Reputation: Monitor sender reputation using tools like Google Postmaster Tools and take proactive steps to address any negative feedback or issues. Reduce spam complaints by ensuring relevant and desired content.
  • Unsubscribe Options: Provide clear and easily accessible unsubscribe options in all bulk emails to comply with regulations and reduce spam complaints.
  • Avoid Blocklists: Adhere to email best practices to avoid being added to blocklists. If listed, promptly take corrective actions and request delisting.
  • Content Review: Review email content for suspicious elements or spam triggers that could increase the likelihood of emails being flagged as spam.
Technical article

Documentation from Spamhaus shares that being listed on a major blocklist due to spam activity can cause ISPs to filter or block emails from your domain or IP address.

November 2024 - Spamhaus
Technical article

Documentation from DMARC.org explains that implementing a DMARC policy tells receiving mail servers what to do with emails that fail SPF and DKIM checks, helping to prevent domain spoofing and phishing attacks.

December 2023 - DMARC.org
Technical article

Documentation from RFC Editor shares that proper SPF, DKIM, and DMARC records help ISPs verify that emails are actually coming from the domain they claim to be, reducing the likelihood of being flagged as spam.

July 2024 - RFC-Editor
Technical article

Documentation from Google explains that emails can go to spam if they are unsolicited, contain suspicious content, aren't authenticated, or are sent from a server with a poor reputation.

September 2021 - Google
Technical article

Documentation from Microsoft responds that bulk senders should ensure they have clear unsubscribe options, manage their sender reputation, and monitor complaint rates to avoid being flagged as spam.

October 2023 - Microsoft

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