Is there a hard limit for IPs on SNDS?

Microsoft does not publicly state a hard maximum for the number of IP addresses allowed on SNDS. However, based on community experience, a practical or unofficial limit of around 5,000 IPs per account has been observed. Large CIDR blocks can often be added successfully by submitting requests for smaller segments within the range.

What happens if I try to add too many IPs to SNDS?

If you attempt to add too many IPs to a single SNDS account, it's generally reported that the system will explicitly notify you that you've reached a limit, rather than silently omitting some of your IPs. This notification allows you to adjust your strategy, perhaps by using multiple accounts or submitting IPs in smaller batches.

Can I monitor CIDR blocks instead of individual IPs?

Yes, SNDS allows you to monitor CIDR blocks (e.g., /24, /19) in addition to individual IP addresses. For large IP ranges, submitting the entire block is the most efficient way to get your IPs covered. This is particularly useful for email service providers or large enterprises with extensive IP infrastructure.

Why would someone need multiple SNDS accounts?

Some organizations manage extremely large volumes of IP addresses that may exceed the practical limit of a single SNDS account. In such cases, using multiple SNDS accounts allows for the comprehensive monitoring of all IP ranges, segmenting them across different accounts to ensure full visibility and management.

How does SNDS help with email deliverability?

SNDS provides critical data on how Microsoft's systems perceive your email sending IPs. It offers insights into spam complaints, junk mail reporting, and whether your IPs are listed on a blocklist (or blacklist). This data enables you to identify and address deliverability issues proactively, helping you maintain a positive sender reputation and ensure your emails reach the inbox.

What is the maximum number of IPs allowed on SNDS? - Tools - Email deliverability - Knowledge base

Many email senders rely on Microsoft's Smart Network Data Services (SNDS) to monitor their IP reputation and ensure high deliverability to Outlook.com and Hotmail.com inboxes. A common question arises regarding the maximum number of IP addresses one can register and monitor within SNDS. While there isn't a widely published hard limit from Microsoft, practical observations and community discussions provide insights into what's feasible and recommended for effective email deliverability management.

SNDS is a crucial tool for anyone sending email volume to Microsoft recipients. It offers valuable insights into how your IP addresses are perceived by Microsoft's email infrastructure, including spam complaints, junk mail reporting, and blocklist (or blacklist) status. Without this visibility, diagnosing deliverability issues to Microsoft domains would be significantly more challenging.

The data provided by SNDS helps senders understand the health of their sending IPs and take proactive steps to maintain a positive sender reputation. Monitoring your IP activity through SNDS is as essential as monitoring your data from Google Postmaster Tools to ensure broad inbox placement.

Understanding the perceived limits

While Microsoft does not publicly state a hard maximum for the number of IP addresses you can register on SNDS, community observations suggest practical limits. Some users have reported successfully registering thousands of IPs, well into the 3,000 range. However, there's a commonly cited informal limit of around 5,000 IP addresses per SNDS account.

It's important to note that when adding IP addresses, especially large ranges, SNDS might process them in batches. For instance, the documentation for Twilio's SendGrid integration with SNDS mentions that you can only request access for 20 IPs at a time. If you need to add more, you would typically wait for the first set to be processed before adding the next batch. This indicates an internal processing queue rather than a strict upper limit on total IPs.

For very high-volume senders, the number of IPs needed can quickly escalate, especially when considering how many IPs are needed per million emails sent daily. In such cases, managing large CIDR blocks, such as a /19 (which represents 8,192 IP addresses), within SNDS has been successfully implemented by some organizations, often by submitting access requests per /24 block within that larger range.

Overcoming perceived limits

If you manage a very large number of IPs, or encounter the informal 5,000 IP threshold, there are workarounds. A common strategy for organizations with extensive IP ranges is to utilize multiple SNDS accounts. This allows for segmentation of IP monitoring and can help ensure that all your active sending IPs are being tracked, even if a single account has a practical limitation.

The process for adding users to Microsoft SNDS for multiple accounts involves verifying ownership of the IP ranges for each account. This distributed approach can be more complex to manage but provides comprehensive monitoring for large IP portfolios.

It is crucial that if you have a significant number of IPs, you aim to get them all listed. Unmonitored IPs can silently accrue negative reputation, leading to deliverability issues that you might only discover through bounce messages or recipient complaints, rather than proactive monitoring through SNDS.

Impact on deliverability and reputation

Regardless of the exact number of IPs you manage, consistent monitoring through SNDS is vital for maintaining a healthy email program. If your IPs get listed on a blocklist (or blacklist), your emails may be delayed, quarantined, or rejected outright. SNDS provides early warnings for such issues specifically for Microsoft properties.

A key takeaway is that an explicit numerical limit is less important than ensuring all your sending IPs are under observation. Even a single IP becoming blacklisted can impact the deliverability of an entire pool if not addressed promptly. Understanding what happens when your IP gets blocklisted and having the data to quickly remediate is paramount.

Monitoring small IP ranges

For senders with a few dedicated IPs or smaller IP pools, direct management through a single SNDS account is typically sufficient. You can easily add and monitor each IP, gaining granular insights into its performance without encountering any practical limits.

The focus here remains on diligently reviewing complaint rates, spam trap hits, and IP status. Immediate action can be taken if an IP shows signs of trouble, such as being placed on a blocklist or receiving high complaint volumes.

Monitoring large IP ranges

Organizations sending very high volumes across extensive IP infrastructure (e.g., hundreds or thousands of IPs) need a more strategic approach. While a single SNDS account may accommodate a significant number, managing them across multiple accounts or by adding entire CIDR blocks can be necessary.

The challenge shifts from simply adding IPs to automating the monitoring and alert process across a vast IP space. Ensuring no IP is left unmonitored is critical to prevent unexpected deliverability drops caused by a single problematic IP within a large block.

Best practices for IP management with SNDS

To effectively leverage SNDS, regardless of your IP volume, adhere to these best practices:

Verify ownership: Always ensure you verify ownership of your IP ranges in SNDS to gain access to your data. This is a fundamental step for all IPs you intend to monitor.
Monitor actively: Don't just add your IPs and forget about them. Regularly review your SNDS data for trends, spikes in complaints, or changes in blocklist status. Proactive monitoring helps you address issues before they escalate.
Segment IPs: If you send different types of email (e.g., transactional, marketing), consider segregating your IP addresses. This helps isolate potential reputation issues to specific sending streams.
Warm up new IPs: New IPs require a gradual warmup process to build a positive sending reputation before reaching full volume. SNDS data can help you track their initial performance.

By following these guidelines, you can ensure that your IP addresses are properly monitored and that you're equipped to handle any deliverability challenges that may arise.

Final thoughts on SNDS IP management

While there isn't a published hard cap on the number of IP addresses allowed on SNDS, practical experience indicates a potential soft limit, often cited around 5,000 IPs per account. For organizations with larger IP portfolios, managing these through multiple SNDS accounts or submitting requests for broader CIDR blocks can facilitate comprehensive monitoring.

The key takeaway for senders is not to focus solely on a maximum number, but rather on ensuring that all IP addresses sending email to Microsoft recipients are registered and actively monitored within SNDS. Proactive reputation management and quick remediation of any blocklist (or blacklist) issues are crucial for maintaining strong deliverability.

Views from the trenches

Best practices

Regularly check your SNDS account and logs to confirm all your IP ranges are actively monitored and reporting data.

Segment your IP addresses by email type (e.g., transactional, marketing) to isolate potential reputation issues.

Implement a robust IP warming strategy for all new IPs added to SNDS to build a positive sending reputation.

Common pitfalls

Not verifying if all IPs are actually being monitored due to an unseen or uncommunicated limit.

Overlooking smaller IP ranges or individual IPs, assuming they won't impact the overall pool's reputation.

Relying solely on bounce messages for deliverability issues instead of proactive SNDS monitoring.

Expert tips

For managing exceptionally large volumes of IPs, consider using multiple SNDS accounts to ensure comprehensive coverage and avoid potential internal limitations.

Utilize automated tools or scripts to pull SNDS data for large IP sets, making monitoring more efficient.

Always register your entire CIDR block where possible, even if it contains many IPs, as SNDS is designed to handle ranges.

Expert view

Expert from Email Geeks says: While there's no published hard limit, some users report practical limitations on the number of IPs you can have in one SNDS account, possibly around 5000 IPs.

2018-12-19 - Email Geeks

Marketer view

Marketer from Email Geeks says: My experience shows that you can successfully list a significant number of IPs, even large CIDR blocks like /19 (8,000 IPs), without issues, as long as requests are submitted per /24.

2018-12-19 - Email Geeks