Summary
Despite good click-to-open rates, emails can land in Hotmail/Outlook's spam folder due to a complex interplay of factors. Microsoft's filtering technologies consider sender reputation, user engagement, authentication, content, and sending patterns. Even with high average open rates, a segment of unengaged users, content triggers, and poor authentication can negatively impact deliverability. Being blacklisted and unusual sending patterns are also contributing factors.
Key findings
- Spam Foldering and Engagement: Emails might be going to the spam folder because a segment of users aren't engaging, despite overall good open rates. User engagement is weighted heavily by Microsoft.
- Sender Reputation Matters: Even with engaged recipients, sender reputation, potentially affected by associations with problematic websites or aggressive mailing, plays a vital role.
- Authentication is Key: Proper configuration of SPF, DKIM, and DMARC is essential for email authentication. Without these, emails are more likely to be flagged as spam.
- Content Can Trigger Filters: The content of your emails, including spam trigger words, excessive links, or poor HTML structure, can trigger spam filters.
- List Hygiene is Critical: Maintaining a clean and engaged email list by removing inactive subscribers can significantly improve deliverability.
- Blacklisting Impacts Deliverability: Being blacklisted by real-time blackhole lists (RBLs) will directly impact the deliverability to Microsoft domains.
- Microsoft's Ambiguous Responses: Microsoft saying 'no issues' can often mean that your emails are being correctly filtered as spam.
- Microsofts filtering technologies: Outlook.com uses filtering technologies to identify and separate unwanted email, even if the emails appear legitimate
Key considerations
- Monitor Sender Score: Regularly check your sender score and IP reputation to identify and address any potential issues.
- Audit Email Content: Review your email content for spam trigger words, excessive links, and ensure proper HTML structure to avoid triggering spam filters.
- Implement Proper Authentication: Implement SPF, DKIM, and DMARC authentication to verify the authenticity of your emails and improve deliverability.
- Practice List Segmentation: Segment your email lists based on engagement and implement a sunset policy to remove or re-engage inactive subscribers.
- Check for Blacklisting: Regularly check your IP address and domain against various RBLs to ensure you are not blacklisted.
- Monitor Sending Patterns: Ensure that you have established a normal email sending rate, as abnormal sending patterns may be filtered as spam.
- Junk Email Reporting Program: Sign up for Microsofts JMRP(Junk Email Reporting Program) so users can report false positives.
- Domain Reputation: Manage domain reputation, addressing any potential associations with problematic or untrustworthy websites to improve deliverability and increase user engagement.
What email marketers say
6 marketer opinions
Even with good click-to-open rates, emails can still land in the spam folder in Hotmail/Outlook due to factors beyond recipient engagement. Sender reputation, content triggers, authentication issues, and list hygiene significantly influence Microsoft's complex spam filtering algorithms. A segment of unengaged users can negatively impact deliverability, even with generally good open rates. Blacklisting, spam trigger words and poor HTML content can all impact deliverability.
Key opinions
- Sender Reputation: Hotmail/Outlook considers sender reputation as a major factor, influencing deliverability irrespective of good click-to-open rates.
- Content Triggers: Certain keywords, excessive links, or poor HTML structure within the email body can trigger spam filters.
- Authentication: Improperly configured SPF, DKIM, and DMARC records can lead to emails being marked as spam.
- List Hygiene: A segment of unengaged users within the email list can negatively impact deliverability, even with good overall open rates.
- Blacklisting: IP addresses or domains may be blacklisted, leading to delivery issues specifically with Hotmail/Outlook.
Key considerations
- Check Sender Score: Regularly monitor sender score and IP reputation to identify and address any potential issues.
- Review Email Content: Scrutinize email content for spam trigger words, excessive links, and ensure proper HTML structure.
- Verify Authentication: Ensure SPF, DKIM, and DMARC records are correctly configured and validated.
- Segment and Suppress: Segment email lists based on engagement and suppress or re-engage inactive subscribers.
- Monitor Blacklists: Check IP addresses and domains against various RBLs to identify potential blacklisting.
- IP Warming: Warm up IP addresses to increase email sending rates over time to improve reputation.
Marketer view
Email marketer from Mailjet Blog explains that even with good engagement, Hotmail/Outlook may filter emails to spam due to factors like sender reputation, content triggers, or authentication issues. They suggest checking sender score, reviewing email content for spam triggers, and ensuring proper SPF, DKIM, and DMARC records are set up.
16 Jan 2025 - Mailjet Blog
Marketer view
Email marketer from Email Geeks Forum suggests that even with good average open rates, a portion of unengaged users can hurt your reputation with Microsoft. Implement a sunset policy to remove or re-engage inactive subscribers.
30 Mar 2025 - Email Geeks Forum
What the experts say
4 expert opinions
Despite good click-to-open rates, Hotmail/Outlook may filter emails to the spam folder due to several factors. Spam foldering, stemming from lower engagement from some users, can negatively impact deliverability, and is often related to maintaining a clean email list. Potential reputation issues may also be related to mailing domains. According to experts in the field, Microsoft support stating that there are no problems could mean the mail is being correctly filtered as spam.
Key opinions
- Spam Foldering: A portion of your emails might be going directly to the spam folder, impacting overall engagement metrics and deliverability.
- User Engagement Emphasis: Hotmail/Outlook prioritizes user engagement, and low engagement from a segment of recipients can trigger spam filters despite high overall open rates.
- Reputation Issues: Reputation problems related to aggressive mailing practices or associations with problematic websites can lead to delivery issues.
- List Hygiene: Mailing to old or uninterested email addresses damages sender reputation and increases the likelihood of emails landing in the spam folder.
- Microsoft 'No issues': When Microsoft support advises that there are no issues, this can be a sign the mail is being correctly filtered as spam.
Key considerations
- List Management: Regularly clean your email list to remove unengaged users to maintain a healthy sender reputation.
- Engagement Monitoring: Monitor engagement metrics and implement a sunset policy to re-engage or remove inactive subscribers.
- Domain Reputation: Assess and manage domain reputation, addressing any potential associations with problematic or untrustworthy websites.
- Content Quality: Ensure your content is relevant and targeted to prevent disengagement and increase the likelihood of recipients marking your emails as spam.
- Check Spam Folder: Manually check spam folder and look for issues with content of the emails.
Expert view
Expert from Email Geeks suggests several reasons for Microsoft delivery issues including potential reputation problems with Spokeo's website and aggressive mailing to Office365 tenants. Also states that Microsoft saying “Don’t see any issues” is Microsoft speak for “your mail is being correctly filtered as spam”.
23 Jan 2023 - Email Geeks
Expert view
Expert from Email Geeks suggests that the drop in opens at Hotmail could be due to spam foldering. The click-to-open rate is consistent, which suggests a fraction of the mail is going to the spam folder.
25 Aug 2022 - Email Geeks
What the documentation says
3 technical articles
Even with good click-to-open rates, emails can still land in spam folders due to filtering technologies, sender reputation, unusual sending patterns, and improper email authentication. Microsoft's Outlook.com uses various filtering methods to identify unwanted emails. Standards like SPF, DKIM, and DMARC are critical for proper email authentication and avoiding spam folders. IP reputation, user spam reports, and authentication setup can impact delivery, regardless of good open rates.
Key findings
- Filtering Technologies: Outlook.com uses filtering technologies to identify and separate unwanted email, even if the emails appear legitimate.
- Sender Reputation: Sender reputation is a crucial factor influencing whether emails are filtered, regardless of click-to-open rates.
- Authentication Standards: SPF, DKIM, and DMARC are vital for proper email authentication and improving deliverability.
- IP Reputation: IP reputation and user spam reports significantly impact email delivery.
- Unusual Sending Patterns: Unusual sending patterns are a reason emails may still be filtered, even if authentication is in place.
Key considerations
- Monitor Sending IP: Use the Junk Email Reporting Program (JMRP) and Sender Information Data Access (SIDA) to monitor your sending IP.
- Implement SPF, DKIM, DMARC: Ensure SPF, DKIM, and DMARC are properly configured to enhance email authentication.
- Monitor IP Reputation: Regularly check and maintain a good IP reputation to avoid being flagged as spam.
- Avoid Spam Triggers: Ensure that you are following best practices to avoid having your emails marked as spam.
- Check Sending Patterns: Ensure you are not deviating from regular sending patterns as this may cause emails to be marked as spam.
Technical article
Documentation from RFC-Editor provides information on implementing SPF, DKIM and DMARC. These are technical standards that improve the chances of avoiding spam folders and improving email authentication. Poor configuration of these will mean your emails are likely to go to the junk folder.
27 Nov 2023 - RFC-Editor
Technical article
Documentation from Microsoft Postmaster explains that Outlook.com uses filtering technologies to identify and separate unwanted email. Even if emails seem legitimate, there are a number of reasons emails may still be filtered, like sender reputation or unusual sending patterns. It advises senders to use the Junk Email Reporting Program (JMRP) and Sender Information Data Access (SIDA) to monitor their sending IP.
9 Oct 2022 - Microsoft Postmaster
Can the sender name impact email delivery to spam in Hotmail/Outlook?
Does UCE Protect Level 3 at an ESP affect delivery to major ISPs like Hotmail or Office 365?
How can I improve email deliverability with Microsoft and avoid spam filters?
How can I improve my sender reputation and inbox placement with Microsoft?
How do I get my emails out of spam for Hotmail and Outlook?
How to fix Hotmail/Outlook emails landing in spam even with proper authentication and opt-in?
