Summary
Emails may not reach Microsoft inboxes due to a complex interplay of factors. These include Microsoft's aggressive filtering, poor IP and sender reputation, authentication failures (SPF, DKIM, DMARC), spam triggers in email content, low user engagement, negative feedback loops, shared IP issues, inadequate technical infrastructure, and sudden sending volume spikes. Addressing these requires a multi-pronged approach encompassing monitoring sender reputation via SNDS/JMRP, ensuring correct email authentication, actively managing subscriber lists, warming up IP addresses, testing email content, gradually increasing sending volume, using dedicated IPs, proper technical configuration, monitoring feedback loops, improving user engagement, and being prepared to engage Microsoft support for mitigation, even when faced with seemingly arbitrary blocks.
Key findings
- Aggressive Filtering: Microsoft's email filtering is known to be particularly stringent.
- Reputation is Critical: Both IP and sender reputation significantly impact deliverability.
- Authentication is Key: Proper implementation of SPF, DKIM, and DMARC is essential.
- Content Matters: Email content is scanned for spam triggers.
- Engagement Impacts Delivery: Low user engagement (opens, clicks) negatively affects deliverability.
- Shared IPs Can Hurt: Using shared IPs can lead to problems due to other senders' practices.
- Infrastructure Must Be Sound: Proper technical infrastructure (reverse DNS, HELO/EHLO) is required.
- Volume Requires Ramp-Up: Sudden sending volume spikes can trigger spam filters.
- Microsoft Mitigation Needed: Sometimes, contacting Microsoft support is necessary for issue resolution.
Key considerations
- Monitor Reputation Tools: Actively monitor tools like SNDS and JMRP to track reputation.
- Implement Email Authentication: Ensure SPF, DKIM, and DMARC are correctly configured and functioning.
- Clean and Manage Lists: Regularly clean email lists and remove inactive or unengaged subscribers.
- Warm Up IPs: Gradually warm up new IP addresses to build reputation slowly.
- Test Content: Thoroughly test email content for spam triggers and potential issues.
- Control Sending Volume: Avoid sudden sending volume spikes; increase volume gradually.
- Consider Dedicated IPs: If possible, use dedicated IPs to control reputation.
- Maintain Technical Infrastructure: Ensure all aspects of technical infrastructure are correctly configured.
- Monitor Feedback Loops: Monitor feedback loops to identify and address spam complaints.
- Improve User Engagement: Focus on improving user engagement with your emails.
- Engage Microsoft Support: Be prepared to contact Microsoft support when encountering persistent issues.
What email marketers say
9 marketer opinions
Emails may fail to deliver to Microsoft inboxes due to various factors, including low engagement, negative feedback from recipients, shared IP addresses, inadequate infrastructure setup, spam triggers in content, sudden volume spikes, and DMARC policy failures. Improving deliverability involves cleaning email lists, monitoring feedback loops, using dedicated IPs, ensuring proper technical configuration, testing content, gradually increasing sending volume, warming up IP addresses, and correctly configuring SPF/DKIM.
Key opinions
- Low Engagement: Low open and click rates negatively impact deliverability. Cleaning lists and segmenting audiences improves engagement.
- Negative Feedback: User complaints (spam reports) hurt deliverability. Removing complaining users is crucial.
- Shared IP Issues: Shared IPs can be problematic due to the actions of other senders. Dedicated IPs improve sender reputation.
- Infrastructure Problems: Inadequate infrastructure (reverse DNS, HELO/EHLO) causes issues. Proper configuration is essential.
- Spam Triggers: Spam keywords and formatting trigger filters. Content testing is necessary.
- Volume Spikes: Sudden volume increases can trigger filtering. Gradual warming up is advised.
- DMARC Failures: DMARC policies can cause rejection. Correct SPF/DKIM setup is vital.
Key considerations
- Engagement Improvement: Implement strategies to increase email engagement (opens, clicks) to signal positive sender reputation.
- Feedback Monitoring: Actively monitor feedback loops and promptly address complaints to minimize negative impact.
- IP Reputation: Consider switching to a dedicated IP and warm up it correctly to control sender reputation more effectively.
- Technical Setup: Ensure correct technical configuration of email sending infrastructure, including reverse DNS and HELO/EHLO.
- Content Optimization: Test email content for spam triggers and optimize formatting to avoid triggering filters.
- Sending Volume Management: Gradually increase sending volume to build trust and avoid triggering spam filters.
- Authentication Implementation: Implement and correctly configure SPF, DKIM, and DMARC authentication to verify email legitimacy.
- Deliverability Testing: Implement deliverability testing to ensure content is not flagged and monitor rates.
Marketer view
Email marketer from Mailjet advises monitoring feedback loops (FBLs) provided by Microsoft to understand if recipients are marking emails as spam. They suggest promptly removing users who complain from email lists to prevent future deliverability problems.
25 Nov 2023 - Mailjet
Marketer view
Email marketer from Email Marketing Forum shares that Microsoft is sensitive to sudden spikes in email volume from new or unestablished senders. They suggest gradually increasing sending volume to build a positive sender reputation over time.
13 Oct 2021 - Email Marketing Forum
What the experts say
9 expert opinions
Emails may not deliver to Microsoft inboxes due to aggressive filtering, IP address blocks, spam filtering, and sender reputation issues. Addressing these issues involves checking IP reputation, ensuring proper email authentication (SPF, DKIM, DMARC), monitoring sender reputation through tools like SNDS, and engaging with Microsoft support for mitigation. It's crucial to ensure everything is technically correct, manage subscriber lists, and understand that Microsoft sometimes blocks emails for seemingly arbitrary reasons.
Key opinions
- Aggressive Filtering: Microsoft employs aggressive filtering techniques, making delivery challenging.
- IP Address Blocks: IP address blocks can prevent delivery; mitigation requires contacting Microsoft.
- Spam Filtering Factors: Microsoft considers content, reputation, and user engagement in spam filtering.
- Sender Reputation: Maintaining a good sender reputation is crucial for successful delivery.
- Technical Correctness: Ensuring all technical aspects are correct is essential, though not a guarantee.
- Arbitrary Blocks: Microsoft may block emails for seemingly arbitrary reasons.
Key considerations
- Reputation Monitoring: Monitor sender reputation using tools like SNDS to identify and address issues.
- Authentication Implementation: Ensure proper email authentication (SPF, DKIM, DMARC) to improve deliverability.
- Technical Audit: Conduct a thorough technical audit to ensure all settings are correct.
- Engagement with Microsoft: Be prepared to engage with Microsoft support to request mitigation and resolve blocks.
- Subscriber List Management: Actively manage subscriber lists to remove inactive users and improve engagement metrics.
- Persistence: Be persistent when seeking mitigation, providing clear reasons for why IPs should be mitigated.
Expert view
Expert from Email Geeks advises ensuring everything is technically correct, as even seemingly minor issues can impact delivery.
27 Nov 2024 - Email Geeks
Expert view
Expert from Spam Resource explains that Microsoft's filtering can be aggressive, and suggests checking your sending reputation and ensuring proper authentication (SPF, DKIM, DMARC). He also highlights that Microsoft sometimes blocks emails for seemingly arbitrary reasons, and engaging with their support can be necessary.
29 Jun 2024 - Spam Resource
What the documentation says
5 technical articles
Email delivery issues to Microsoft inboxes stem from factors like IP reputation, content filtering, authentication failures (SPF, DKIM, DMARC), and sender reputation. Microsoft's SmartScreen filter considers these and user complaints. Key solutions include monitoring SNDS and JMRP, ensuring proper email authentication, avoiding spam traps, actively managing email lists, and having a valid reverse DNS record.
Key findings
- IP Reputation: Poor IP reputation is a significant cause of delivery problems.
- Authentication Failures: SPF, DKIM, and DMARC authentication failures lead to delivery issues.
- Content Filtering: Microsoft's SmartScreen filters emails based on content and other factors.
- Sender Reputation: Maintaining a good sender reputation is crucial for inbox placement.
- Reverse DNS: A valid reverse DNS record is important for establishing trust.
Key considerations
- Monitor SNDS/JMRP: Regularly monitor SNDS data and the Junk Mail Reporting Program to identify issues.
- Implement Authentication: Ensure proper SPF, DKIM, and DMARC configuration to authenticate emails.
- Manage Email Lists: Actively manage email lists to remove inactive subscribers and avoid spam traps.
- Check Reverse DNS: Verify that your sending IP address has a valid reverse DNS record.
- Avoid Spam Traps: Take steps to avoid sending emails to spam trap addresses.
Technical article
Documentation from AuthSMTP explains that maintaining a good sender reputation is crucial for successful email delivery to Microsoft. They recommend consistently authenticating emails (SPF, DKIM, DMARC), avoiding spam traps, and actively managing email lists to remove inactive subscribers.
15 May 2023 - AuthSMTP
Technical article
Documentation from RFC editor highlights that having a valid reverse DNS record (PTR record) that matches the sending IP address to the sending domain is an important part of creating trust in mail systems and that this improves deliverability.
31 Oct 2024 - RFC-Editor
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