What’s the difference between IP vs domain reputation in SNDS?

Microsoft's Smart Network Data Services (SNDS) is a free diagnostic tool that shows you how Outlook.com and Hotmail see your sending infrastructure. If you've looked at it and wondered exactly what's being measured, you're not alone. The answer matters more than it seems.

SNDS reports IP reputation, not domain reputation. Every metric you see in the dashboard (the traffic light status, complaint rates, spam trap hits) is tied to a specific IP address. If you send from three IPs, you get three separate profiles.

Microsoft does track domain reputation internally, but that data doesn't appear in SNDS. Domain signals feed into SmartScreen filtering alongside IP data, so they influence whether your emails land in the inbox. You just can't see that side of the equation through SNDS directly.

Why does this matter in practice? It depends on how you send.

• Shared IP senders need to remember that SNDS data reflects everyone on that IP pool, not just your list. A bad actor sharing your IP can drag your SNDS rating down even when your own sending is clean.
• Dedicated IP senders see a clean picture of their own behavior. If your SNDS is red, it's on you (which is actually easier to fix).

The most useful thing to do with SNDS data is treat it as an early warning system. A yellow or red status before you notice inbox placement problems is your cue to check complaint rates, look for spam trap exposure, and review which campaigns ran during that window. If you're on a shared IP and the data looks worse than your list quality should explain, it's worth asking your ESP whether you're co-mingled with senders who have poor practices.

Want to see whether your domain has any reputation issues on Microsoft's network? Our free Blocklist Checker can flag infrastructure problems worth investigating alongside your SNDS review.