Summary
SFMC shared IPs face deliverability challenges specifically with Microsoft domains due to several interconnected factors. Microsoft employs aggressive and stringent spam filtering mechanisms, making them highly sensitive to the overall reputation of sending IPs. Shared IPs, by their very nature, inherit the reputation of all users contributing to them. Therefore, even if a sender adheres to best practices, the actions of others on the shared IP can negatively impact deliverability, triggering filters and blocklists. Microsoft's SmartScreen filter evaluates various factors, including IP address, domain, content, and user complaints, making shared IPs particularly vulnerable due to the varied practices of multiple senders. Additional issues include fluctuations in sending volume, inadequate IP warm-up, incorrect SMTP configurations, missing or misconfigured rDNS records, and poor implementation of DMARC policies, which can lead to spoofing and phishing attempts. Moreover, Microsoft's filters are sensitive to content and user engagement metrics, exacerbating the problems for SFMC shared IPs. There also exists the possibility that the quality of mail sent from SFMC shared ranges may have been impacted by the departure of key personnel from the abuse team. Transitioning to a dedicated IP offers greater control over reputation and deliverability.
Key findings
- Microsoft Aggressiveness: Microsoft utilizes aggressive spam filtering techniques, placing a high emphasis on sender IP reputation.
- Inherited Reputation: Shared IPs inherit the reputation of all senders, making them susceptible to negative impact from others' poor practices.
- SmartScreen Evaluation: Microsoft's SmartScreen filter analyzes IP address, domain, content, user complaints, and more, increasing vulnerability for shared IPs.
- Technical Configuration: Incorrect SMTP configurations, missing rDNS records, and inadequate DMARC implementation can trigger Microsoft's filters.
- Content and Engagement: Microsoft's filters are sensitive to content, user engagement metrics, and complaint rates.
- SFMC Challenges: SFMC shared IP users face the challenge of issues outside their control.
- Poor IP warm up: If SFMC does not warm up IPs this causes deliverability challenges.
Key considerations
- Proactive Monitoring: Continuously monitor IP reputation, deliverability metrics, and blocklist status.
- Best Practices: Adhere to email sending best practices to minimize negative impact on IP reputation.
- DMARC Implementation: Implement and maintain proper DMARC policies to prevent spoofing and phishing attempts.
- Technical Audit: Regularly audit SMTP configurations, rDNS records, and other technical settings.
- Relationship with SFMC: Communicate and collaborate with SFMC to address shared IP issues and potential solutions.
- Long-Term Strategy: Consider migrating to a dedicated IP address for greater control over sending reputation.
- Engagement: Implement strategies to improve engagement from your recipients to demonstrate you are a legitimate sender.
What email marketers say
14 marketer opinions
SFMC shared IPs often face deliverability issues with Microsoft domains due to several factors. Microsoft employs aggressive filtering techniques, making them particularly sensitive to IP reputation. Shared IPs, by their nature, inherit the reputation of all senders using them, meaning that poor sending practices from even a few users can negatively impact the entire IP range. Microsoft also monitors sending volume, consistency, content, user engagement, and feedback loops. Improper IP warmup, blocklist appearances, incorrect SMTP configurations, and the lack of proper DMARC implementation can further exacerbate deliverability problems. The departure of key members from SFMC's abuse team may have also contributed to a decline in the overall quality of mail sent from their shared ranges.
Key opinions
- Aggressive Filtering: Microsoft's filtering is known to be more aggressive, impacting shared IPs disproportionately.
- Shared IP Reputation: Shared IPs inherit the reputation of all senders, making them vulnerable to the actions of others.
- Volume and Consistency: Fluctuations in sending volume from shared IPs can trigger Microsoft's spam filters.
- Blocklist Impact: SFMC shared IPs are more likely to appear on blocklists, hindering deliverability to Microsoft domains.
- Content Sensitivity: Microsoft's content filters are sensitive to certain keywords and phrases, affecting deliverability.
- User Engagement: Low user engagement (e.g., marking emails as spam) from SFMC shared IPs can lead to blocks.
- IP Warmup: Improper or insufficient IP warmup on SFMC shared IPs worsens deliverability issues.
- Feedback Loops: High complaint rates from Microsoft users can result in SFMC shared IPs being blocked.
- SMTP Configuration: Incorrect SMTP configuration on SFMC shared IPs causes deliverability problems with Microsoft.
- DMARC: If SFMC does not implement DMARC policies correctly then it affects deliverability to Microsoft.
Key considerations
- Reputation Monitoring: Consistent monitoring of IP reputation is crucial for identifying and addressing deliverability issues.
- Content Optimization: Carefully review and optimize email content to avoid triggering Microsoft's spam filters.
- User Engagement Strategies: Implement strategies to improve user engagement and reduce spam complaints.
- IP Warmup Process: Ensure a proper IP warmup process when using shared IPs or transitioning to new IPs.
- DMARC Implementation: Implement correct DMARC policies.
- SFMC Support: Engage with SFMC support to address underlying issues with shared IP reputation and configuration.
Marketer view
Email marketer from Reddit shares that Microsoft's filtering is known to be more aggressive, and shared IPs often bear the brunt of this. Even if your email practices are clean, others on the shared IP could be negatively impacting your deliverability to Microsoft domains.
26 Jul 2024 - Reddit
Marketer view
Email marketer from Litmus mentions that Microsoft pays close attention to user engagement metrics. If recipients frequently mark emails from SFMC shared IPs as spam or delete them without reading, Microsoft's filters will learn to block those IPs.
1 Sep 2021 - Litmus
What the experts say
4 expert opinions
Experts suggest that Microsoft's aggressive spam filtering, combined with the inherent challenges of shared IP reputation, leads to deliverability issues for SFMC shared IPs. Microsoft's sensitivity to IP reputation means that even if a user's sending practices are sound, the behavior of others on the shared IP can negatively impact deliverability. Furthermore, SFMC may not actively address these issues unless there's a direct financial incentive. Ultimately, experts recommend transitioning to a dedicated IP for better control over reputation or ensuring contract terms offer mitigation for deliverability problems.
Key opinions
- Microsoft's Aggression: Microsoft's spam filters are aggressive and require ongoing vigilance.
- Shared IP Vulnerability: Shared IPs are susceptible to the actions of other senders, affecting overall reputation.
- SFMC Inaction: SFMC may not prioritize addressing deliverability issues without a direct financial incentive.
- Dedicated IP Benefits: A dedicated IP offers greater control over sending reputation and deliverability.
Key considerations
- IP Strategy: Consider the long-term strategy for IP management, including potential migration to a dedicated IP.
- Contract Review: Review SFMC contracts for guarantees or mitigations against deliverability problems.
- Proactive Monitoring: Implement proactive monitoring of IP reputation and deliverability metrics.
- Reputation Management: Prioritize maintaining a good sending reputation through best practices and compliance.
Expert view
Expert from SpamResource explains that Microsoft tends to be more sensitive to the overall reputation of shared IPs. This is because shared IPs are used by multiple senders, increasing the likelihood that some senders may engage in practices considered less desirable by Microsoft, leading to filtering issues.
29 Nov 2022 - SpamResource
Expert view
Expert from Word to the Wise explains that Maintaining a good sending reputation is vital for reaching your audience's inboxes. It’s much easier to maintain a good reputation on a dedicated IP than on a shared IP where you have less control over the sending behavior and reputation of the IP.
1 Feb 2025 - Word to the Wise
What the documentation says
5 technical articles
Documentation from various sources highlights that SFMC shared IPs experience deliverability issues with Microsoft domains due to a combination of factors. Microsoft's SmartScreen filter evaluates sender reputation based on multiple elements, and shared IPs are prone to reputation damage from other senders' actions. Inadequate DMARC implementation on shared IPs increases the risk of spoofing and phishing, leading to stricter filtering by Microsoft. Furthermore, misconfigured reverse DNS records on shared IPs can negatively impact deliverability. The use of shared IP pools by SFMC, where some senders may not adhere to best practices, exacerbates these problems. Poor practices will impact deliverability across all major ISPs due to decline in IP reputation.
Key findings
- SmartScreen Reputation: Microsoft's SmartScreen filter considers IP address, domain, content, and user complaints.
- Shared IP Risk: Shared IPs are vulnerable to reputation damage due to the actions of multiple senders.
- DMARC Impact: Poor DMARC implementation on shared IPs increases the risk of spoofing and stricter filtering.
- rDNS Issues: Misconfigured reverse DNS records on shared IPs negatively affect deliverability.
- Shared IP Pools: SFMC's use of shared IP pools can lead to deliverability problems if senders don't follow best practices.
- General IP Reputation: Poor shared IP practices will degrade IP reputation across multiple ISPs.
Key considerations
- DMARC Implementation: Implement and maintain proper DMARC policies to protect against spoofing.
- rDNS Configuration: Ensure correct configuration of reverse DNS records for shared IPs.
- Sender Practices: Adhere to email sending best practices to minimize reputation damage.
- IP Strategy: Consider migrating to a dedicated IP address for greater control over reputation.
- Monitor IP Health: Routinely monitor IP reputation to determine if there are any immediate actions required to stop your decline.
Technical article
Documentation from Google explains that While focusing on Microsoft, it's important to note the interconnectedness of deliverability. Google's postmaster tools illustrate how IP reputation is a crucial factor for all major ISPs. Poor practices on a shared IP affecting Microsoft deliverability are likely to impact deliverability to other providers as well, due to a general decline in IP reputation.
4 Mar 2023 - Google
Technical article
Documentation from DMARC.org describes if senders using shared IPs do not properly implement DMARC (Domain-based Message Authentication, Reporting & Conformance) policies, it can increase the chances of email spoofing and phishing attacks originating from those IPs. Microsoft is more likely to block or filter emails from IPs with poor DMARC implementation.
6 Nov 2022 - DMARC.org
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