Does Microsoft SNDS monitor reputation for Office 365 hosted domains?
Michael Ko
Co-founder & CEO, Suped
Published 24 Jul 2025
Updated 19 Aug 2025
9 min read
Microsoft's email ecosystem can seem complex, especially when you're trying to understand how various tools monitor email reputation. One common question revolves around whether Microsoft's Smart Network Data Services (SNDS) provides reputation data for domains hosted on Office 365. This is a point of frequent misunderstanding for many email senders, particularly those who rely on email service providers (ESPs) or third-party hosting.
When I first started looking into this, I noticed a clear distinction in how different providers offer their postmaster tools. For instance, Google Postmaster Tools offers insights into reputation for gmail.com addresses and domains hosted within Google Workspace (formerly G Suite). It’s a comprehensive tool for those sending to Google users.
However, the situation with Microsoft SNDS is a bit different. My experience, along with what I've gathered from other email professionals, indicates that SNDS primarily focuses on the reputation of sending IP addresses delivering mail to Microsoft's consumer mail properties, such as Outlook.com, Hotmail.com, and Live.com. This distinction is crucial for understanding where to focus your monitoring efforts.
The scope of Microsoft SNDS
SNDS provides valuable data for senders to monitor their IP reputation. This service offers high-level insights into email deliverability and sender behavior for emails directed at Microsoft's consumer-facing email services. It helps identify issues like spam activities, sudden spikes in traffic, or low complaint rates, which are all indicators of your sending health. You can see your IP status (green, yellow, or red) and analyze various metrics.
The primary goal of SNDS is to help email senders understand how their traffic is perceived by Microsoft's global network of consumer mail servers. This includes detailed information about complaint rates and potential blocklist (or blacklist) listings that affect Outlook.com, Hotmail, and other similar domains. For example, if a large number of recipients mark your emails as spam, SNDS will reflect this through increased complaint rates and a degraded IP status.
It's important to remember that SNDS is fundamentally an IP-based reputation tool. While your domain's reputation is intrinsically linked to the IPs you send from, SNDS's direct reporting primarily concerns the IP addresses. This means if you're using an ESP or a shared IP pool, the data you see in SNDS will reflect the collective sending behavior of all users on those IPs, not just your specific domain's activity in isolation.
Focus
Provides insights for @gmail.com users and domains hosted on Google Workspace.
Tracks both IP and domain reputation metrics.
Focus
Primarily offers data for IP reputation impacting Outlook.com, Hotmail.com, and Live.com domains.
Does not directly monitor domain reputation for Office 365 hosted domains.
Outlook.com versus Office 365 hosted domains
This is where much of the confusion lies. Many people tend to conflate Outlook.com (the consumer email service) with Office 365 (now Microsoft 365, the enterprise cloud suite). While they are both Microsoft products and may share underlying technologies, their email handling and reputation monitoring systems are distinct in how they interact with SNDS. The key takeaway from my observations and discussions with peers is that SNDS specifically covers the consumer-facing domains, not business domains hosted on Office 365.
Office 365 (or Microsoft 365) domains are typically custom domains managed by organizations for their business email. For example, if your company uses example.com, and your emails are hosted by Office 365, then emails sent to your recipients at example.com are filtered differently than emails sent to @outlook.com addresses. Microsoft handles spam filtering and reputation for Office 365 environments using its Exchange Online Protection (EOP) service. EOP employs its own sophisticated set of rules, including content filtering, sender authentication checks (like SPF, DKIM, DMARC), and other proprietary algorithms to determine inbox placement.
Therefore, while your sending IPs might appear "green" in SNDS, this status only reflects your standing with Microsoft's consumer mail services. It does not directly translate to or guarantee inbox placement for emails sent to domains hosted on Office 365. For example, a business recipient at a company using Office 365 might still see your emails land in spam, even if SNDS shows a perfect reputation for your IPs. This is a common scenario that can be quite frustrating for senders.
Understanding the distinction
Outlook.com/Hotmail/Live.com: These are Microsoft's consumer email services. SNDS primarily provides reputation data for emails delivered to these domains.
Office 365 (Microsoft 365): These are business email services hosting custom domains (e.g., yourcompany.com). Email filtering for these domains is handled by Exchange Online Protection (EOP), which uses a broader set of criteria beyond just IP reputation reported by SNDS.
Domain reputation and IP reputation in Office 365
For Office 365 hosted domains, the emphasis shifts from purely IP reputation, as seen in SNDS, to a more holistic view that heavily weighs domain reputation. Microsoft's Exchange Online Protection (EOP) evaluates numerous factors for business-to-business (B2B) email deliverability. This includes your domain's authentication records (SPF, DKIM, DMARC), historical sending patterns, recipient engagement, and content quality. If your domain is new or has a low volume, you might encounter initial deliverability challenges, even if your underlying IPs are clean.
When troubleshooting deliverability issues to Office 365 recipients, it’s essential to look beyond SNDS. My first steps usually involve verifying all email authentication records. An incorrect or missing SPF record, a misconfigured DKIM signature, or a DMARC policy that isn't properly enforced can significantly impact your emails' ability to reach the inbox of Office 365 users. You can review our guide on how to fix common DMARC issues in Microsoft 365 and Google Workspace for detailed steps.
Furthermore, Microsoft's anti-spam algorithms, including their proprietary blocklists (blacklists), are constantly evolving. They track sender behavior, spam complaints, and even URL reputation within the email content. If you're sending from an IP address or domain that has a history of spamming, or if your emails contain malicious links, you're likely to face blockages. It is crucial to have strong security practices to prevent your systems from being compromised, which could lead to your IPs being listed on a blocklist.
SPF record example for Office 365plaintext
v=spf1 include:spf.protection.outlook.com -all
Monitoring Office 365 deliverability
Since SNDS doesn't directly cover Office 365 hosted domains, how do you effectively monitor your email deliverability to these critical recipients? The answer lies in a multi-pronged approach that goes beyond a single tool. It requires diligent monitoring of your overall sending health and proactive adherence to best practices for email authentication and engagement.
Firstly, ensure your domain has robust email authentication protocols in place. This includes SPF, DKIM, and DMARC. These records help recipient servers verify that your emails are legitimate and authorized, significantly improving your chances of reaching the inbox. Microsoft heavily relies on these standards, and their absence or misconfiguration can lead to emails being marked as spam or blocked outright. For instance, sometimes Microsoft O365 will mark emails as spam even if they are sent from a third-party ESP if there are issues with authentication.
Secondly, pay close attention to engagement metrics for your campaigns. Microsoft's filtering algorithms, especially EOP, factor in how recipients interact with your emails. Low open rates, high delete rates without opening, or frequent spam complaints will negatively impact your sender reputation with Office 365. Encourage recipient engagement, make it easy to unsubscribe, and regularly clean your email lists to remove inactive or invalid addresses. You can also gain insight into common issues with Microsoft SNDS that affect deliverability.
Finally, while SNDS doesn't cover Office 365 directly, it still provides a useful proxy for your general reputation with Microsoft. If your SNDS metrics show a declining trend, it's a strong indicator that your overall sending practices need attention, which will likely affect your Office 365 deliverability as well. Combine this with feedback loops, bounce reports, and general deliverability testing to get a comprehensive view.
Monitor both IP and domain health beyond SNDS for Office 365 deliverability.
Consistently ensure all email authentication standards like SPF, DKIM, and DMARC are correctly implemented.
Maintain clean email lists and encourage positive recipient engagement to improve sender reputation.
Regularly review bounce reports and feedback loops for insights into deliverability issues.
Understand the distinction between consumer-facing Outlook.com and business-focused Office 365 filtering.
Common pitfalls
Solely relying on SNDS data for Office 365 deliverability can lead to overlooked issues.
Neglecting domain-level authentication leads to poor inbox placement even with clean IPs.
Sending to unengaged recipients or purchased lists significantly harms sender reputation.
Failing to address spam complaints and blacklists (blocklists) quickly impacts overall email health.
Assuming Outlook.com and Office 365 have identical filtering mechanisms.
Expert tips
Implement a DMARC policy at p=quarantine or p=reject to protect your domain and improve deliverability.
Use a dedicated IP for high-volume sends to better control your sending reputation.
Engage with Microsoft's support channels if you face persistent deliverability challenges to Office 365.
Conduct regular email deliverability tests using diverse seed lists, including Office 365 targets.
For shared IPs, understand the ESP's reputation management practices and request dedicated IPs if issues persist.
Marketer view
Marketer from Email Geeks says they found it confusing whether SNDS monitored reputation for Office 365 hosted domains, as their clients often use ESPs and don't own their sending IP addresses.
2019-09-25 - Email Geeks
Expert view
Expert from Email Geeks says that SNDS is exclusively for Outlook.com hosted domains, clarifying the distinction from Office 365.
2019-09-26 - Email Geeks
Navigating Microsoft's email ecosystem
In summary, Microsoft SNDS is a valuable resource for monitoring the IP reputation of mail sent to Microsoft's consumer-facing domains like Outlook.com, Hotmail.com, and Live.com. However, it does not directly provide reputation data for domains hosted on Office 365 (Microsoft 365). These enterprise environments are primarily managed by Exchange Online Protection (EOP), which evaluates a broader set of factors including domain authentication, content, and engagement.
To ensure strong deliverability to Office 365 recipients, focus on implementing and maintaining robust email authentication protocols (SPF, DKIM, DMARC), cultivating positive sender behavior, and closely monitoring your overall domain reputation. Understanding these distinctions is key to successful email deliverability in Microsoft's diverse ecosystem.
Google Workspace.
Outlook.com, Hotmail.com, and Live.com domains.
Microsoft products and may share underlying technologies, their email handling and reputation monitoring systems are distinct in how they interact with SNDS. The key takeaway from my observations and discussions with peers is that SNDS specifically covers the consumer-facing domains, not business domains hosted on Office 365.
