Outlook and Hotmail represent over 350 million active accounts worldwide. If you send an email to these addresses, Microsoft SNDS is the only way to see how their filters perceive your sending:
- Spam trap hits
- Volume and transmission data
- Filter results (green, yellow, or red status)
- Complaint rates from users marking mail as junk
Unlike Google Postmaster Tools, SNDS is entirely IP-based — you need dedicated IP ownership to use it. The filter results are intentionally vague (Microsoft doesn’t want to help spammers), and most senders misunderstand what the colors actually mean.
In this article, we’ll explore how to use Microsoft SNDS to keep an eye on your Outlook’s deliverability.
What is Microsoft SNDS?
Smart Network Data Services is a free monitoring platform from Microsoft that shows how their systems view traffic from your IP addresses.
The data comes directly from Microsoft’s inbound mail server logs, giving you visibility into how your sending reputation stands with one of the world’s largest mailbox providers.
SNDS tracks several metrics for each verified IP:
- Spam trap hits
- SMTP command data (RCPT, DATA, HELO)
- Message volume and transmission success
- Complaint percentages from junk mail reports
- SmartScreen filter verdicts (the green/yellow/red status)
The tool covers only consumer Microsoft domains: outlook.com, hotmail.com, live.com, and msn.com. Business accounts — Office 365, Exchange Online, Microsoft 365 — operate under different systems and aren’t included.
Senders with dedicated IPs targeting consumer Microsoft addresses should consider SNDS essential. ESPs and high-volume marketers benefit most because the tool requires IP ownership verification through WHOIS records. If you’re on shared IPs through your email provider, you can’t access SNDS directly — your ESP manages that visibility.
Anyone troubleshooting Outlook or Hotmail deliverability issues needs the data SNDS provides. Without it, you’re guessing about why Microsoft might be filtering your mail.
How do you set up Microsoft SNDS?
Setup requires proving you control the IP addresses you want to monitor. The process takes anywhere from minutes to days, depending on your IP registration status.
Request access
Navigate to sendersupport.olc.protection.outlook.com/snds and sign in with a Microsoft account (Hotmail or Outlook works fine). Click “Request Access” and enter your IP addresses or CIDR ranges. You can submit up to 20 IPs at a time — for larger ranges, you’ll need multiple requests.
Verify ownership
Microsoft sends a verification email to the abuse contact listed in your IP’s WHOIS record. Before requesting access, confirm your WHOIS registration shows a valid, monitored abuse@ address.
Click the authorization link in the email from Microsoft to complete verification.
If your WHOIS data is outdated or points to your hosting provider rather than your organization, verification becomes more complex. You may need to coordinate with your provider or update your IP registration first.
Wait for data
After verification, dashboards remain empty until you send at least 100 messages per day to Microsoft domains. Data appears within a day or two of reaching that threshold. SNDS retains 90 days of historical data, so you can track trends over time. Seeing nothing immediately after setup usually means insufficient volume — not a configuration error.
What do the filter results mean?
The filter results show how Microsoft’s SmartScreen content filter views your mail. Colors indicate the percentage of messages receiving a “spam” verdict. The system is straightforward on the surface but deceptive in its implications.
| Color | Spam verdict | Interpretation |
| Green | Less than 10% | Most mail trusted |
| Yellow | 10-90% | Borderline — investigate |
| Red | More than 90% | Serious reputation problem |
Green status
Less than 10% of your mail is flagged as spam by SmartScreen. Good news, but don’t assume green means inbox placement. SmartScreen’s verdict is one factor among many — user behavior (moving mail to junk, ignoring messages) can override filter decisions. A green IP can still have mail landing in spam folders if recipients consistently disengage.
Yellow status
Somewhere between 10% and 90% of mail is flagged. Microsoft keeps this range deliberately vague — they don’t want spammers gaming the system with precise thresholds.
During IP warming, yellow status is common and not necessarily alarming. New IPs often show yellow until sufficient positive volume establishes a reputation.
If yellow persists alongside declining open rates for Microsoft domains, reduce volume and investigate. Check recent content changes, list hygiene, and authentication setup. The ambiguity is frustrating (intentionally so), but treating yellow as a warning sign is the right approach.
Red status
More than 90% of mail is flagged as spam. Your IP has a serious reputation problem with Microsoft. Recovery takes days to weeks of consistent, low-volume, high-quality sending. There are no shortcuts — you’ll need to reduce volume immediately, clean your list aggressively, and wait for your reputation to rebuild.
The critical distinction
Filter results don’t directly equal inbox or spam folder placement. SmartScreen’s verdict tells you how the filter classified your mail, not where it ultimately landed.
User engagement, personal filters, and individual behavior all influence final placement. A red IP can occasionally reach inboxes (if recipients whitelist you), and green IPs can still hit spam folders (if recipients ignore your mail).
Treat filter results as a temperature reading, not a diagnosis.
What other metrics should you monitor?
Beyond filter results, SNDS provides several data points that help diagnose sending problems.
Complaint rate
The fraction of recipients marking your mail as junk. Microsoft calculates this as complaints divided by message recipients — a direct measure of user dissatisfaction.
| Rate | Assessment |
| Below 0.1% | Healthy |
| 0.1% – 0.5% | Concerning |
| Above 0.5% | Serious problem |
Complaints feed directly into the sender’s reputation. Unlike filter results (which reflect automated decisions), complaints represent actual user action — someone deliberately marking your email as unwanted. High complaint rates damage reputation faster than almost any other signal.
Trap hits
Spam trap addresses your IP has hit. The number should be zero. Any hits indicate list hygiene problems — purchased lists, scraped addresses, or subscribers who abandoned email addresses that became traps.
Microsoft doesn’t reveal which addresses are traps, so you can’t simply remove them. You’ll need to clean your entire list of unengaged and unverified addresses.
RCPT vs DATA gap
RCPT commands show recipients that your server attempted to reach. DATA commands show messages actually transmitted.
A large gap between these numbers indicates high rejection or bounce rates — Microsoft is refusing mail before delivery completes.
Calculate the difference — if RCPT shows 1,000 and DATA shows 900, you have 100 rejected messages. Investigate list quality and validation processes. Remove hard bounces immediately.
Sample messages
SNDS provides one sample message per IP per type per day. Click on daily data to access examples of flagged mail. These samples reveal what content or patterns triggered filtering — useful for diagnosing why SmartScreen is flagging your sends.
HELO/EHLO command
The identifier your mail server sends at SMTP session start. The HELO value should match your sending domain configuration. Mismatches can signal misconfiguration or suspicious behavior. If your HELO looks off in SNDS, verify your mail server settings align with your domain.
What is JMRP, and how does it connect?
The Junk Mail Reporting Program is Microsoft’s feedback loop for spam complaints. When an Outlook or Hotmail user marks your email as junk, JMRP sends a copy of that message to a designated address you control.
JMRP feeds are now linked to SNDS accounts — you can’t set up the feedback loop without first registering your IPs in SNDS. To configure JMRP, navigate to the Junk Mail Reporting Program page within the SNDS portal and create a new feed.
The setup requires:
- Company name and contact email
- Complaint format (ARF is standard)
- Complaint feedback email address (where reports will arrive)
- Maximum complaints per day (set high to avoid missing data)
Be cautious with the feedback address — if you set limits too low or point reports to a regular mailbox, you’ll either miss complaints or overwhelm your inbox. JMRP is designed for automated processing, not manual review.
The feedback loop only covers consumer Microsoft domains. Corporate Exchange environments operate under different systems without public feedback loops.
What should you do when metrics look bad?
Seeing problems in SNDS is only useful if you know how to respond. Each metric requires different remediation.
Red filter result
Immediate action required:
- Review recent content for spam triggers
- Check authentication (SPF, DKIM, DMARC)
- Reduce sending volume to Microsoft domains
- Wait — recovery takes days to weeks of consistent positive sending
- Audit list hygiene — remove bounces, inactive subscribers, unverified addresses
Don’t panic about a single red day, but a persistent red status requires aggressive intervention.
High complaint rate
Recipients are telling Microsoft your mail is unwanted. Review email content and sending frequency. Check unsubscribe visibility — if recipients can’t find your unsubscribe link, they’ll use the spam button instead.
Segment disengaged subscribers and either reduce frequency or remove them entirely. Monitor JMRP reports for patterns that reveal which campaigns generate complaints.
Trap hits
Your list contains addresses that should never receive email. Clean purchased or scraped addresses immediately. Remove subscribers with no engagement over 6+ months. Validate your list before sending. Tighten opt-in processes to prevent invalid addresses from entering in the first place.
RCPT/DATA gap
Microsoft is rejecting mail before delivery completes — usually indicating list quality issues.
- Validate email addresses before sending via an email validation API.
- Check for syntax errors or typos in your list
- Remove hard bounces immediately
If the gap persists, your list may contain too many invalid or problematic addresses.
What are the limitations?
SNDS provides valuable data but has significant blind spots worth understanding.
The tool covers consumer Microsoft domains only — no visibility into Office 365, Exchange Online, or any Microsoft 365 business accounts. If your audience is primarily B2B, SNDS tells you almost nothing useful.
IP-based monitoring excludes shared IP senders. If you send through an ESP’s shared IP pool, you can’t access SNDS directly. Your ESP may provide aggregate data, but individual sender visibility is limited.
The minimum threshold of 100 messages per day means low-volume senders won’t see data. The yellow range of intentionality is vague, making precise diagnosis difficult. Filter results don’t equal actual inbox placement — they show SmartScreen’s verdict, not final delivery location.
SNDS has no alerts or notifications. You’ll need to check manually and regularly. Set a calendar reminder or integrate with monitoring tools that pull SNDS data automatically.
For complete visibility, combine SNDS with Google Postmaster Tools for Gmail and inbox placement testing across all providers.
To sum it up
SNDS shows how Microsoft’s filters view your IP — valuable data you can’t get anywhere else, but only one piece of the deliverability picture.
Combine with Gmail monitoring and cross-provider inbox testing for complete visibility (you can use an email deliverability checker to do that).
If SNDS reveals problems you can’t diagnose, an email deliverability consultant can help translate the metrics into an action plan.
Frequently asked questions
Here are some commonly asked questions about using Microsoft SNDS:
Volume is below 100 messages per day to Microsoft domains, or your IP isn’t fully verified. Check that verification completed successfully and increase sending volume to Microsoft addresses.
No. SNDS only tracks consumer domains — outlook.com, hotmail.com, live.com, msn.com. Business accounts on Office 365, Exchange Online, and Microsoft 365 aren’t included.
No. SNDS requires dedicated IP ownership and verification through WHOIS abuse contacts. Shared IP senders need to work through their ESP for Microsoft reputation visibility.
Weekly for routine monitoring. Daily, when troubleshooting deliverability issues or during IP warming. SNDS has no built-in alerts, so manual checks are essential.
Yes. New IPs commonly show yellow until sufficient positive sending volume establishes a reputation. Monitor actual open rates for Microsoft domains alongside SNDS status — if engagement stays healthy, yellow during warming is expected.
