Track your IP reputation with Outlook, Hotmail, and Live.com, and get alerted the moment Microsoft flags your sending infrastructure.
Microsoft SNDS (Smart Network Data Services) is the reputation system Microsoft uses to decide how to handle mail for Outlook, Hotmail, Live.com, and MSN addresses. Every sending IP gets a color rating: green (good), yellow (caution), or red (bad). A red rating effectively blocks delivery to one of the largest consumer mail ecosystems on the planet.
SNDS is not a public DNSBL. It is Microsoft's internal reputation system, exposed only through the SNDS portal and available only to registered senders. The data includes complaint rates, spam trap hits, filter results, and message volume, updated daily.
An SNDS listing will rarely appear on any public blacklist. A sender can pass every RBL check cleanly while their Microsoft reputation quietly degrades. Without specific SNDS monitoring, the first signal is usually a customer support ticket asking why Outlook mail stopped delivering.
The reputation signals that predict Microsoft delivery problems.
Track transitions between green, yellow, and red. Any movement toward yellow or red triggers an alert.
Monitor the percentage of mail flagged by recipients. A rising complaint rate is an early warning before it affects your rating.
Microsoft maintains honeypot addresses. Any traffic to them indicates list hygiene problems that will degrade reputation.
Unlike most blacklists, SNDS has no delisting request. Microsoft updates ratings as its systems see changes in sender behavior. Getting back to green requires fixing the underlying problem (complaint spike, spam trap activity, sudden volume change), maintaining good behavior for several days, and waiting for Microsoft's systems to recognize the correction. SNDS monitoring gives you the visibility to know whether corrective action is working before it shows up in bounce logs.
For context on how SNDS fits alongside other reputation systems, see the Complete Guide to Email Blacklist Monitoring. For general email deliverability diagnostics, the Email Health Check on Mr. DNS grades SPF, DMARC, and MTA-STS configuration.
Smart Network Data Services (SNDS) is Microsoft's internal reputation system for Outlook, Hotmail, Live.com, and MSN. Every sending IP receives a color rating (green, yellow, or red) based on complaint rates, spam trap hits, filter results, and message volume. A red rating effectively blocks delivery to Microsoft's consumer mail infrastructure.
Microsoft updates SNDS data daily. Generator Labs monitors each registered IP on an ongoing schedule and alerts on any transition toward yellow or red, so you see degradation before it becomes a delivery problem.
No. Unlike most blacklists, SNDS does not have a delisting request. Microsoft updates ratings automatically as its systems observe changes in sender behavior. Recovery requires fixing the underlying cause (complaint rate, spam trap hits, volume anomalies) and maintaining good behavior for several days.
An SNDS issue rarely appears on any public RBL. A sender can pass every DNSBL check cleanly while their Microsoft reputation quietly degrades. Without specific SNDS monitoring, the first signal is a customer support ticket asking why Outlook delivery stopped.
SNDS monitoring is included with every Generator Labs RBL Monitoring plan, alongside hundreds of other data sources. Free tier available.