Summary
Gmail's rejection of emails from Microsoft accounts is a multifaceted issue influenced by factors such as domain/IP reputation, IPv6 misconfigurations, aggressive spam filtering, and the exploitation of default DKIM domains. Documentation highlights the importance of adhering to email standards and best practices, while experts note that Gmail treats IPv6 reputation differently and holds it to higher standards. To improve deliverability, it is crucial to monitor sender reputation, properly configure IPv6, ensure email authentication, and comply with sending policies.
Key findings
- Reputation: Gmail rejects emails based on domain and IP reputation, often due to spam activity associated with Microsoft accounts or IP ranges.
- IPv6: Improper IPv6 configuration and the use of shared IPv6 addresses significantly impact deliverability to Gmail due to stricter reputation checks.
- Authentication: Lack of proper email authentication (SPF, DKIM, DMARC) results in emails being flagged as spam or rejected by Gmail.
- Exploitation: Exploitation of default DKIM domains in G Suite and O365 contributes to deliverability problems.
- Filtering: Gmail's aggressive spam filtering mistakenly blocks legitimate emails from Microsoft accounts.
Key considerations
- Monitor Reputation: Regularly monitor your IP and domain reputation using tools like Google Postmaster Tools and MXToolbox.
- Configure IPv6: Ensure proper IPv6 configuration or revert to IPv4 if deliverability issues persist with IPv6.
- Implement Authentication: Implement and verify SPF, DKIM, and DMARC records to authenticate your emails.
- Review Sending Practices: Review and adhere to both Gmail's and Microsoft's sending policies to avoid being flagged as spam.
- Dedicated IP: Consider using a dedicated IP address, especially for IPv6, to improve sender reputation.
- Address Fundamental Issues: Tools like Return Path Certification can help but will not solve fundamental sending and list management problems.
What email marketers say
9 marketer opinions
Gmail's rejection of emails from Microsoft accounts is often attributed to domain and IP reputation issues, particularly when sending via IPv6. Aggressive spam filtering, shared IP addresses, and misconfigured IPv6 setups can lead to deliverability problems. Ensuring proper email authentication (SPF, DKIM, DMARC), monitoring sender reputation, and adhering to Gmail's and Microsoft's sending policies are crucial for improving email delivery rates. Google Postmaster Tools and MXToolbox can aid in diagnosing and resolving these issues.
Key opinions
- Reputation: Gmail rejects emails from Microsoft accounts due to low domain or IP reputation, often linked to spam activity.
- IPv6 Issues: Improperly configured IPv6 settings and shared IPv6 addresses can negatively impact deliverability to Gmail.
- Spam Filtering: Gmail's aggressive spam filters may mistakenly block legitimate emails from Microsoft accounts.
- Authentication: Lack of proper email authentication (SPF, DKIM, DMARC) can lead to email rejection by Gmail.
Key considerations
- Check Blocked Status: Verify if your Outlook.com account or IP address is blocked by Gmail.
- Authentication Setup: Implement and verify SPF, DKIM, and DMARC records to authenticate your emails.
- Monitor Reputation: Regularly monitor your sender reputation using tools like Google Postmaster Tools and MXToolbox.
- IPv6 Configuration: Ensure proper configuration of IPv6 settings, or consider using IPv4 if IPv6 deliverability is problematic.
- Dedicated IP: Using a dedicated IP address, especially for IPv6, can improve deliverability.
- Review Policies: Comply with both Gmail's and Microsoft's sending policies to avoid being flagged as spam.
Marketer view
Marketer from Email Geeks shares information about Google (Gmail) rejecting email from Microsoft accounts due to a "domain reputation issue." The issue was specific to Microsoft sending to Gmail via IPv6, with Google detecting these emails as spam to protect their end users. Both Google and Microsoft have acknowledged the issue, and the sender she worked with is now able to deliver to Gmail.
13 May 2025 - Email Geeks
Marketer view
Email marketer from Google Support explains that Gmail might reject emails if the sender is blocked or marked as spam. They advise checking the blocked senders list and ensuring that the sender isn't inadvertently marked as spam.
24 Dec 2024 - Google Support
What the experts say
5 expert opinions
Experts indicate that Gmail's rejection of emails from Microsoft accounts, particularly those sent over IPv6, is often due to reputation differences between IPv4 and IPv6, infrastructure reputation issues, and the exploitation of default DKIM domains. Gmail holds IPv6 mail to higher standards, and Microsoft's IP ranges may suffer from a bad reputation due to spam. While tools like Return Path certification can assist with deliverability, fundamental sending practices must be addressed first.
Key opinions
- IPv6 Reputation: Gmail treats IPv6 reputation differently than IPv4 reputation, requiring careful configuration and monitoring.
- Infrastructure Reputation: Delivery problems from Microsoft or Google, and not elsewhere, often indicate an infrastructure reputation issue.
- DKIM Exploitation: Exploitation of default DKIM domains in G Suite and O365 contributes to deliverability problems.
- Higher Standards: Google holds mail over IPv6 to higher standards, contributing to potential rejection.
Key considerations
- IPv6 Configuration: Carefully configure and monitor IPv6 settings to maintain a good reputation.
- Address Sending Practices: Ensure proper email authentication, content quality, and list hygiene.
- Avoid DKIM Exploitation: Do not exploit default DKIM domains to avoid damaging your own domain reputation.
- Infrastructure Review: Review and improve your email infrastructure to maintain a positive sending reputation.
Expert view
Expert from Spamresource explains that Gmail treats IPv6 reputation differently than IPv4 reputation. Sending from a shared IPv6 address or with poor IPv6 setup can negatively impact deliverability to Gmail. While not impossible, sending email to Gmail over IPv6 requires careful configuration and monitoring.
23 Mar 2024 - Spamresource
Expert view
Expert from Word to the Wise explains that Return Path certification (now Validity) can help improve deliverability to Gmail and other providers, but doesn't solve fundamental sending issues. It acts more like a 'fast pass' once other deliverability issues (authentication, content, list hygiene) are properly addressed.
24 Feb 2024 - Word to the Wise
What the documentation says
5 technical articles
Email delivery issues from Microsoft accounts to Gmail are influenced by factors detailed in various documentation sources. While RFCs outline fundamental email protocols and message formatting standards, they don't specifically address IPv6 or Gmail's filtering mechanisms. Google Postmaster Tools emphasizes the role of IP and domain reputation in spam filtering, with IPv6 misconfigurations contributing to poor reputation. Microsoft Docs suggests checking sender reputation, DNS configuration, and adhering to sending policies. The IETF documentation highlights that IPv6 implementation can affect email deliverability based on server configurations.
Key findings
- Reputation Matters: Gmail uses IP and domain reputation to filter spam, as highlighted by Google Postmaster Tools.
- IPv6 Impact: IPv6 misconfigurations can lead to poor IP reputation and subsequent email rejection, as noted by both Google and IETF documentation.
- Standard Protocols: Basic email transmission and formatting standards are defined in RFCs but don't address modern filtering practices.
- Policies and Configuration: Following Microsoft's sending policies and ensuring proper DNS configuration are crucial for deliverability, according to Microsoft Docs.
Key considerations
- Monitor Reputation: Regularly monitor IP and domain reputation using tools like Google Postmaster Tools.
- Configure IPv6 Correctly: Ensure proper configuration of IPv6 settings to avoid deliverability issues.
- Adhere to Policies: Comply with both Gmail's and Microsoft's sending policies to avoid being flagged as spam.
- Review DNS Settings: Verify and correct DNS settings to ensure proper email routing and authentication.
Technical article
Documentation from RFC Editor details the original SMTP (Simple Mail Transfer Protocol) standards, which govern how email is transmitted across the internet. It outlines basic requirements for message formatting and delivery, though it doesn't specifically address IPv6 or Gmail's filtering practices.
29 May 2024 - RFC Editor
Technical article
Documentation from Microsoft Docs outlines troubleshooting steps for email delivery issues from Microsoft accounts. It suggests checking sender reputation, ensuring proper DNS configuration, and following Microsoft's sending policies to avoid being flagged as spam by Gmail.
3 Mar 2023 - Microsoft Docs
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