Why are Microsoft email deliverability issues unusually bad right now?

Summary

Microsoft email deliverability issues are unusually challenging due to a confluence of factors. Many senders are experiencing blocks and deliverability problems, even with established reputations. Underlying causes include poor sender reputation stemming from spam complaints, low engagement, sending to inactive email addresses, and technical setup issues like incorrect SPF, DKIM, and DMARC records. Microsoft's adaptive filtering systems respond to user behavior, so engagement metrics are crucial. Additional factors include sudden volume spikes without proper IP warming, poor list hygiene, content quality, potential IP blacklisting, and the complexity of Microsoft's filtering algorithms. Addressing these issues requires a multi-faceted approach, including implementing strong authentication (SPF, DKIM, DMARC), actively monitoring and improving engagement, practicing consistent list hygiene, carefully managing sending volumes, and closely monitoring sender reputation.

Key findings

  • Reputation is Paramount: Sender reputation, influenced by engagement, complaints, and list quality, significantly impacts deliverability to Microsoft.
  • Authentication is Essential: Proper SPF, DKIM, and DMARC implementation is critical for verifying sender identity and message integrity.
  • Microsoft's Adaptive Filters: Microsoft's filtering system is adaptive and responsive to user behavior, making engagement a key signal.
  • Volume Matters: Sudden volume increases without proper IP warming can trigger spam filters and damage reputation.
  • List Hygiene is Non-Negotiable: Maintaining a clean and engaged email list is essential for positive sender reputation and deliverability.

Key considerations

  • Implement Strong Authentication: Ensure SPF, DKIM, and DMARC are correctly configured for your sending domains.
  • Boost and Monitor Engagement: Actively work to improve email engagement metrics (opens, clicks) and closely monitor user behavior.
  • Practice List Hygiene Regularly: Implement a process for regularly cleaning your email lists to remove inactive, invalid, or unengaged addresses.
  • Warm Up IP Addresses: If using a new IP address, gradually increase sending volume to establish a positive reputation.
  • Monitor Sender Reputation Constantly: Use tools like Microsoft SNDS and third-party services to monitor your IP and domain reputation.

What email marketers say
13Marketer opinions

Microsoft email deliverability is currently facing challenges due to a combination of factors. Senders are experiencing blocks and filtering issues even with previously good reputations. Common causes include poor sender reputation stemming from spam complaints, low engagement, and sending to inactive addresses. Technical setup problems like incorrect SPF, DKIM, and DMARC records are also significant contributors. Additionally, Microsoft's complex filtering algorithms and adaptive systems respond to user behavior, making engagement metrics critical. Other factors include sudden volume spikes, poor list hygiene, content quality, and potential IP blacklisting. Maintaining consistent sending patterns, warming up IP addresses, monitoring sender reputation, and properly authenticating emails are recommended for improvement.

Key opinions

  • Reputation Impact: Poor sender reputation due to spam complaints, low engagement, and inactive addresses affects deliverability.
  • Technical Setup: Incorrect SPF, DKIM, and DMARC records contribute to deliverability issues.
  • Microsoft Algorithms: Microsoft's filtering algorithms and adaptive systems respond to user behavior, heavily influencing deliverability.
  • Volume Spikes: Sudden increases in email volume without proper IP warming can trigger spam filters.
  • List Hygiene: Poor email list hygiene with invalid or inactive addresses negatively impacts sender reputation.

Key considerations

  • Authentication: Implement and verify SPF, DKIM, and DMARC records to authenticate your email sending.
  • Engagement: Monitor and improve email engagement metrics to signal positive sender reputation to Microsoft.
  • List Maintenance: Regularly clean your email list to remove invalid, inactive, or unengaged addresses.
  • Volume Control: Gradually warm up IP addresses and maintain consistent sending volume and frequency.
  • Reputation Monitoring: Monitor your sender reputation and IP blacklists to identify and address deliverability issues proactively.
Marketer view

Email marketer from SendGrid recommends authenticating your emails with SPF, DKIM and DMARC. SendGrid also recommends warming up your IP address, cleaning your email list, segmenting your email list, and monitoring your sender reputation.

September 2023 - SendGrid
Marketer view

Email marketer from GlockApps shares tips to improve deliverability to Outlook and Hotmail, including authenticating your domain with SPF, DKIM, and DMARC, monitoring your IP and domain reputation, and segmenting your email list to send targeted content.

March 2024 - GlockApps
Marketer view

Email marketer from Reddit shares that consistent sending volume and frequency help establish a positive sender reputation. Abrupt changes can trigger spam filters.

August 2023 - Reddit
Marketer view

Email marketer from Neil Patel Blog shares that deliverability issues can be caused by a poor sender reputation due to spam complaints, low engagement, or sending to inactive email addresses. Technical setup problems, such as incorrect SPF, DKIM, and DMARC records, can also cause deliverability problems.

August 2023 - Neil Patel Blog
Marketer view

Email marketer from Mailjet shares that Microsoft blocking emails can be due to several factors including sender reputation, spam content, authentication issues, and high complaint rates. They also mention possible IP blacklisting.

December 2023 - Mailjet
Marketer view

Email marketer from Email Geeks asks about sending to business domains vs freemail, noting differences in 365 and Hotmail/Outlook filtering. Suggests content and blocklist issues.

June 2024 - Email Geeks
Marketer view

Email marketer from Email Geeks explains they've seen Microsoft deliverability issues, with clients experiencing blocks even with good sender reputation. They've resorted to eliminating Microsoft from risky strategies.

January 2024 - Email Geeks
Marketer view

Email marketer from Email Geeks explains that Everest seeding shows more O365 problems. They filtered MS free domains from marketing sends. They advise cleaning data and monitoring stats.

December 2022 - Email Geeks
Marketer view

Email marketer from Litmus explains that email deliverability issues are caused by a complex interplay of factors, including sender reputation, authentication, content quality, engagement, and infrastructure. Senders must actively monitor and manage these factors to ensure their emails reach the inbox.

August 2023 - Litmus
Marketer view

Email marketer from SparkPost notes that Microsoft uses complex algorithms to filter email. Deliverability can be affected by factors like IP reputation, content quality, engagement metrics, and recipient complaint rates.

November 2023 - SparkPost
Marketer view

Email marketer from Reddit shares that they experienced deliverability issues due to a sudden increase in email volume without properly warming up their IP address. Also suggested checking IP blacklists.

October 2021 - Reddit
Marketer view

Email marketer from Email Geeks shares a similar experience, with clients getting blocked repeatedly for short periods.

April 2022 - Email Geeks
Marketer view

Email marketer from ZeroBounce explains that poor list hygiene can cause issues. They advise regularly cleaning your email list to remove invalid or inactive addresses to improve your sender reputation and deliverability.

November 2021 - ZeroBounce

What the experts say
3Expert opinions

Microsoft email deliverability issues are widespread. Microsoft's adaptive filtering system considers user behavior, strongly influencing deliverability. Issues are caused by a combination of factors like sudden volume spikes, poor list hygiene, and negative engagement metrics.

Key opinions

  • Adaptive Filtering: Microsoft's filtering system is adaptive and responds to user behavior, affecting deliverability.
  • Engagement Impact: Engagement (or lack thereof) strongly influences Microsoft's filtering decisions.
  • Combined Factors: Blocking is likely caused by sudden volume spikes, poor list hygiene, and negative engagement metrics.

Key considerations

  • Persist and Engage: Continue efforts to improve deliverability, focusing on boosting engagement.
  • Reduce Risky Data: Clean and refine email lists to remove potentially risky data.
  • Monitor and Adjust: Warm up IP addresses properly and closely monitor sender reputation.
Expert view

Expert from Spam Resource answers that blocking is likely caused by a combination of factors like sudden volume spikes, poor list hygiene, and negative engagement metrics. It's important to warm up IP addresses properly and monitor sender reputation closely.

December 2024 - Spam Resource
Expert view

Expert from Email Geeks responds that Anne is not alone, advising to persist, boost engagement, and reduce risky data.

September 2022 - Email Geeks
Expert view

Expert from Word to the Wise explains that Microsoft's filtering system is adaptive and responds to user behavior, so engagement (or lack thereof) strongly influences deliverability. Sudden changes in sending patterns or negative feedback can lead to filtering problems.

December 2023 - Word to the Wise

What the documentation says
5Technical articles

To ensure email deliverability, particularly to Outlook.com and Gmail, senders must adhere to email authentication standards like SPF, DKIM, and DMARC. These protocols verify the sender's domain and message integrity, helping to prevent email spoofing and phishing. Compliance with email provider policies, maintaining low complaint rates, and following best practices for email content are also crucial. Monitoring sender reputation through tools like Google Postmaster Tools is recommended.

Key findings

  • Authentication is Key: SPF, DKIM, and DMARC are essential for verifying sender identity and message integrity.
  • Compliance Required: Complying with email provider policies and guidelines improves deliverability.
  • Reputation Matters: Maintaining a positive sender reputation reduces the likelihood of emails being marked as spam.

Key considerations

  • Implement Authentication: Set up SPF, DKIM, and DMARC records to authenticate your email domain.
  • Monitor Reputation: Use tools like Google Postmaster Tools to monitor your sender reputation.
  • Follow Best Practices: Adhere to best practices for email content to avoid triggering spam filters.
Technical article

Documentation from DKIM.org explains that DKIM (DomainKeys Identified Mail) is an email authentication system designed to verify the domain name of an email sender and the integrity of the message. DKIM uses cryptographic signatures to allow receiving mail servers to verify that an email message was sent by an authorized sender and has not been altered in transit.

March 2024 - DKIM.org
Technical article

Documentation from Google explains that in order to reach Gmail inboxes, you should authenticate your email, avoid spammy practices, and make it easy for users to unsubscribe. Google recommends monitoring your sender reputation in Postmaster Tools.

October 2023 - Google
Technical article

Documentation from DMARC.org explains that DMARC (Domain-based Message Authentication, Reporting & Conformance) is an email authentication protocol that builds on SPF and DKIM to provide domain owners with control over how their domain is used in email, and provides reporting mechanisms to track email authentication results.

July 2023 - DMARC.org
Technical article

Documentation from RFC explains that SPF (Sender Policy Framework) is an email authentication method designed to detect forging sender addresses during the delivery of email. SPF allows receiving mail servers to check that mail claiming to come from a specific domain is authorized by that domain's administrators.

December 2021 - RFC
Technical article

Documentation from Microsoft explains that to ensure deliverability to Outlook.com, senders must comply with their policies and guidelines, which include using authentication protocols (SPF, DKIM, DMARC), maintaining low complaint rates, and following best practices for email content.

May 2022 - Microsoft