Microsoft SNDS: reading Smart Network Data Services before Outlook filters your mail

Microsoft will show you, IP address by IP address, what its spam filters concluded about yesterday's sending, provided you own the IPs and ask. The program is called Smart Network Data Services, SNDS for short, and it is Microsoft's sender transparency portal for mail arriving at Outlook.com, Hotmail and the other consumer Microsoft mailboxes: a free dashboard where the owner of a sending IP can see filter verdicts, complaint levels and spam-trap hits for that IP's traffic. It is the Outlook-side counterpart to Google's Postmaster Tools, and if Microsoft mailboxes matter to your list, it is data you should be reading before a deliverability incident, not after.

What SNDS is, and whose mail it covers

SNDS reports on mail received by Microsoft's consumer mailbox infrastructure, the Outlook.com family. That scope matters in both directions. It means the data reflects the filter that decides why your mail lands in spam across Microsoft's consumer inboxes. It also means SNDS is not a window into corporate Exchange Online tenants, whose filtering is administered per organization; the sender-side rules for the broader Microsoft ecosystem are collected in the Outlook sender requirements.

Access is organized around IP ownership, not domains. You register a Microsoft account, request the IP addresses or ranges you send from, and Microsoft verifies you are entitled to the data by sending an authorization email to an address associated with the range, typically the abuse, postmaster or WHOIS contact. If you send through an ESP's shared pool, those IPs belong to the provider, and it is the provider that holds SNDS access; your own registration becomes useful when you send from a dedicated IP or your own infrastructure, such as a self-hosted SMTP relay.

Reading the data panels

For each monitored IP and each day it sent enough mail to register, SNDS shows a row of verdicts; Microsoft's SNDS FAQ warns that traffic and spam data may not appear for an IP that sent fewer than 100 messages on a given day. The headline is the filter result, presented as a color: green means the filter disliked little of the IP's mail that day, yellow means a meaningful share was junked, red means most of it was. This guide describes the bands qualitatively rather than repeating cutoff percentages that circulate secondhand. Alongside it sit the complaint rate, the share of recipients who clicked "junk" on your mail (the mechanics of that signal are covered under complaint rate), the count of messages sent to Microsoft's spam traps, and sample message data that can help you identify which stream caused a bad day.

Two readings matter more than any single day. Trend: an IP drifting from green toward yellow is losing sender reputation while there is still time to act. Correlation: a complaint spike that lines up with one campaign date tells you which content or segment to investigate, the same triage you would run for a marketing stream landing in spam. Trap hits deserve special alarm at any level, because traps receive no legitimate mail; hits mean your list hygiene is admitting addresses no human uses, and the fix lives in suppression and acquisition practice such as double opt-in, not in content.

JMRP, the companion program

SNDS shows you aggregate complaint levels; Microsoft's Junk Mail Reporting Program (JMRP) is the actionable half. It is Microsoft's feedback loop: enroll your sending IPs and Microsoft forwards you a copy of each message a recipient marks as junk, so your platform can suppress that recipient immediately. Continuing to mail people who have junked you is one of the most damaging behaviors a filter can observe, so treat JMRP enrollment as part of the same registration exercise. Both programs are free.

What SNDS will not tell you

There is no domain-level reputation view, no inbox-versus-junk placement percentage, and no per-message verdict for mail below the daily volume floor. SNDS also reports observation, not causation: a red day says Microsoft junked your mail, not why. The "why" toolkit is the usual one. Confirm authentication end to end with the email authentication checker, since SPF, DKIM and DMARC failures remove your strongest identity evidence. Check the sending IP against public blocklists with the blacklist checker, because listings and filter verdicts often move together. And run a seed-list placement test if you need to know where mail is actually landing at Microsoft today. For a structured walk through that whole sequence, use the deliverability troubleshooter.

Acting on a bad week

A yellow or red run is a reputation incident, and the recovery sequence mirrors any Outlook-side reputation repair: pause or throttle volume to Microsoft domains rather than pushing through the filter, cut the segments generating complaints, purge unengaged addresses, and rebuild volume gradually, the same ramp discipline described in IP warming. Senders whose problem spans providers should run the full deliverability audit instead of treating Microsoft in isolation, because SNDS is frequently just the first place a general problem becomes visible.

A workable cadence for a healthy program is modest: one weekly glance at the color history for every registered IP, one monthly reconciliation of SNDS complaint levels against the complaint data your sending platform reports, and an immediate check whenever Outlook-domain bounce rates move. Senders running campaigns should also time the glance to their sending calendar, since a quiet IP shows no rows at all below the volume floor and an all-green history may simply mean the IP barely sent. The dashboard costs nothing and reads in under a minute; the expensive version of this information is learning it from a blocklist listing weeks later.

Related guides

• Outlook sender requirements — the rules Microsoft publishes for senders
• Postmaster Tools — Google's equivalent sender-data program, for comparison
• Sending email through Microsoft 365 — the infrastructure side of the Microsoft ecosystem
• Why emails go to spam — the evidence hierarchy behind the verdicts SNDS reports
• Blacklist checker — test the same IPs against public DNSBLs
• Deliverability troubleshooter — structured diagnosis when the dashboard turns red

About this guide

Written by InboxRatio Editorial. Program mechanics, the registration and authorization flow, the 100-message data floor, and the color-coded filter results follow Microsoft's published SNDS documentation and FAQ; JMRP behavior follows Microsoft's postmaster documentation. Where Microsoft does not publish exact thresholds, this guide says so rather than inventing numbers. No vendor sponsorship influences it.

Methodology

InboxRatio's benchmark sends real campaigns through the platforms we review to a controlled seed list and records where each message lands. This guide draws on Microsoft's documentation rather than our measurements; the protocol is in how we test and our source rules in sources.

Last updated

2 October 2026. Microsoft program documentation reviewed quarterly.

Frequently asked questions

What is Microsoft SNDS? Smart Network Data Services, Microsoft's free portal that shows the owner of a sending IP how mail from that IP fared at Outlook.com and the other consumer Microsoft mailboxes: filter verdicts by day, complaint rates, spam-trap hits and sample data.

How do I sign up for SNDS? Create a Microsoft account at the SNDS site, request the IPs or ranges you send from, and complete authorization: Microsoft emails a confirmation to an address tied to the range, such as the abuse or postmaster contact, to verify you control it.

Why does SNDS show no data for my IP? The usual reasons: the IP sent fewer messages to Microsoft that day than the documented 100-message floor, the mail went to corporate Exchange Online tenants rather than consumer mailboxes, or authorization for the range has not completed.

What do the SNDS colors mean? They summarize the filter's verdict on the IP's mail for one day: green for mail that mostly passed, yellow for a meaningful junked share, red for a majority junked. Treat yellow as a warning trend and red as an active incident.

What is the difference between SNDS and JMRP? SNDS is the reporting dashboard; the Junk Mail Reporting Program is Microsoft's feedback loop, which forwards you a copy of each message a recipient marks as junk so you can suppress that address. Serious senders enroll in both.

Does SNDS cover Microsoft 365 business mailboxes? No. SNDS reports on Microsoft's consumer mailbox infrastructure. Filtering for Exchange Online tenants is governed per organization, so treat SNDS as your Outlook.com window and monitor business-domain delivery separately.

Microsoft volunteers the evidence; most senders never open the envelope. Register the IPs, enroll in JMRP, glance at the colors weekly, and when a day turns yellow, start with the email authentication checker and work the sequence before red arrives.