What Is Microsoft SNDS and How Does It Work?

Microsoft Smart Network Data Services (SNDS) is a free service that provides information about email traffic from sending IP addresses to Microsoft's consumer email services, including Outlook.com and Hotmail.

SNDS helps senders understand how Microsoft evaluates email traffic and identify potential issues with sending IP reputation.

For email marketing users, understanding SNDS can help explain some of the factors that affect email delivery. However, SNDS focuses on sending IP addresses rather than individual email marketing accounts or campaigns.

This guide explains how SNDS works, what its data means and how good email marketing practices can support deliverability.

What Is Microsoft SNDS?

Microsoft SNDS provides data about email traffic reaching Microsoft's consumer email services from specific sending IP addresses.

Depending on the available data, SNDS can help senders assess:

• IP reputation and filtering: Indicators that help show how Microsoft's filtering systems assess traffic from a sending IP address.
• Email volume: The volume of email activity associated with an IP address.
• Spam complaints: Information about recipients marking messages as junk.
• Potential sending issues: Indicators that may help identify unusual traffic patterns or reputation concerns.

SNDS is an IP-level monitoring service. It does not provide a complete assessment of an individual campaign or explain every delivery issue.

For more information, visit the official Microsoft SNDS website.

How Does Microsoft SNDS Work?

Microsoft collects information about email traffic reaching its consumer email services and makes relevant data available through SNDS to authorised users.

The general process works as follows:

1. Email traffic is monitored. Microsoft collects information about messages received from sending IP addresses.
2. Data is made available. Authorised users can access the reporting available for their sending IP addresses.
3. Reputation indicators are reviewed. Available information can help identify potential filtering or complaint issues.
4. Potential problems are investigated. Changes in traffic, reputation or delivery performance may require further investigation.

SNDS is one source of information for understanding email deliverability. It does not guarantee inbox placement or identify the cause of every rejected message.

Understanding Microsoft SNDS Data

The information available through SNDS depends on the sending IP address, email activity and Microsoft's reporting criteria.

IP filtering indicators

SNDS has historically used colour-coded indicators to summarise aspects of Microsoft's filtering assessment.

• Green: Generally indicates a more favourable filtering assessment.
• Yellow: May indicate that further investigation is appropriate.
• Red: Indicates a less favourable filtering assessment that warrants attention.

The precise meaning and availability of these indicators may vary with Microsoft's reporting. They should be treated as signals for investigation rather than a complete diagnosis of a delivery issue.

Email volume

Email volume shows how much traffic is associated with a sending IP address.

Unexpected changes in volume may warrant investigation, particularly when they coincide with changes in delivery performance or filtering indicators.

Spam complaints

Complaint information can help identify when recipients are marking messages as junk.

For shared sending IP addresses, complaint activity may reflect messages sent by multiple accounts. IP-level data therefore does not necessarily identify which campaign or sender contributed to a particular issue.

Data availability

SNDS may not display data for an IP address if there is insufficient email activity to meet Microsoft's reporting criteria.

The absence of data does not necessarily indicate a reputation problem.

How Sending IP Reputation Affects Email Deliverability

Sending IP reputation is one of several factors that receiving email providers may consider when deciding whether to accept, filter or deliver a message.

When multiple senders use a shared IP address, their sending activity can contribute to the reputation associated with that IP.

Other factors can also affect delivery, including:

• Domain authentication and alignment.
• Mailing list quality and subscriber consent.
• Spam complaints and unsubscribe activity.
• Recipient engagement and expectations.
• Message content and sending patterns.

A favourable SNDS indicator does not guarantee that messages will reach the inbox. Likewise, an unfavourable indicator does not automatically mean every message from that IP will be blocked.

How to Support Good Email Deliverability

Good email marketing practices can help reduce avoidable delivery problems.

Maintain mailing list quality

Send campaigns to subscribers who have given appropriate consent. Remove invalid email addresses and review inactive subscribers regularly.

Avoid purchased, scraped or otherwise unauthorised mailing lists.

Monitor campaign performance

Review bounce rates, unsubscribes, clicks and other available campaign metrics. Unusual changes may help identify list quality, engagement or delivery issues.

Send relevant content

Make sure campaigns match subscriber expectations and provide useful information. Unexpected or irrelevant messages can lead to more complaints and unsubscribes.

Maintain consistent sending practices

Avoid sudden, unexplained increases in sending volume. Plan campaigns around your audience's expectations and engagement patterns.

Authenticate your sending domain

Configure SPF, DKIM and DMARC correctly for your domain where applicable.

Authentication helps receiving systems verify that messages are authorised. However, successful authentication does not guarantee inbox placement.

Troubleshooting Microsoft Email Delivery Issues

Why are my emails going to junk or being blocked?

Several factors can affect delivery to Outlook.com and Hotmail recipients, including sending IP reputation, domain authentication, recipient engagement, mailing list quality and message content.

If you experience persistent delivery issues, contact Mail Blaze Support with the following information:

• The affected recipient domains.
• The relevant campaign details.
• The approximate sending date and time.
• Any available bounce messages or error codes.

This information can help narrow down the possible causes of the issue.

Can I access SNDS for my Mail Blaze campaigns?

SNDS reporting is based on sending IP addresses, not individual campaigns or email marketing accounts.

If you use Mail Blaze's shared sending infrastructure, you do not need to manage access to the shared sending IP addresses yourself. If you experience delivery issues affecting Microsoft recipients, contact Mail Blaze Support so the issue can be investigated.

Frequently Asked Questions

Is Microsoft SNDS free?

Yes. Microsoft provides SNDS free of charge.

Does SNDS monitor my email marketing account?

No. SNDS primarily provides information about sending IP addresses. It does not provide a complete account-level assessment of individual campaigns.

Does SNDS guarantee inbox placement?

No. SNDS provides information that can help assess sending IP reputation and filtering activity. Inbox placement also depends on factors such as recipient behaviour, message content, authentication and other filtering decisions.

Do I need to register for SNDS to use Mail Blaze?

No. You do not need to register for SNDS to use Mail Blaze's shared sending infrastructure. If you experience delivery issues affecting Microsoft recipients, contact Mail Blaze Support for assistance.

What should I do if my campaigns are not reaching Outlook.com or Hotmail recipients?

Contact Mail Blaze Support and provide the affected recipient domains, campaign details, sending times and any available bounce messages. This information can help with the investigation.

Is SNDS the same as Microsoft's Junk Email Reporting Program (JMRP)?

No. SNDS provides information about sending IP traffic and reputation. JMRP is a separate programme that provides feedback about messages recipients report as junk. Both services are associated with Microsoft's email reporting and reputation tools.