Why are my emails landing in the spam folder for Outlook and Hotmail?
Matthew Whittaker
Co-founder & CTO, Suped
Published 13 Jul 2025
Updated 16 Aug 2025
6 min read
It can be incredibly frustrating when your emails consistently land in the spam or junk folder, especially when sending to Outlook and Hotmail addresses. You've checked your blocklists, confirmed your sending practices, yet messages still don't reach the inbox. This issue is common, and Microsoft's filtering systems are known for their strictness, which can sometimes be difficult to navigate.
We often hear from senders who are puzzled by this behavior, particularly when their emails seem compliant. The reality is that there are many factors at play beyond just being on a public blacklist or blocklist. Microsoft's algorithms consider a wide array of signals to determine inbox placement, from technical configurations to how recipients interact with your mail.
Understanding Outlook and Hotmail filtering
Microsoft, including Outlook and Hotmail, employs sophisticated spam filtering mechanisms that go beyond simple blocklist checks. Their internal reputation system relies heavily on user engagement signals. If recipients frequently delete your emails without opening them, mark them as junk, or simply ignore them, your sender reputation can suffer, leading to future emails landing in the spam folder.
Microsoft assigns a Spam Confidence Level (SCL) to incoming emails. While a low SCL, like 1, might suggest an email isn't spam, it's not the only factor. SCL values range from 0 (low confidence spam) to 9 (high confidence spam). An SCL of 5 or 6 indicates suspected spam, while 9 is considered certain spam. Intermediate SCL ratings (2, 3, 4, 7, 8) are not explicitly set by the service.
The combination of these internal scores, along with user feedback, dictates where your emails land. This is why you might not be on any external blocklist, yet your messages are still being filtered. Microsoft’s system prioritizes the recipient experience, and negative interactions contribute significantly to poor inbox placement.
Technical authentication and reputation
Email authentication is paramount. Failing to properly configure SPF, DKIM, and DMARC can severely impact your deliverability to Microsoft domains. Even if messages are delivered, lack of proper authentication can flag them as suspicious, sending them straight to junk. It's crucial that your sending domain aligns with these authentication protocols.
Furthermore, your IP and domain reputation play a critical role. If you're using a shared IP address from an Email Service Provider (ESP), the sending habits of other users on that IP can affect your deliverability. Microsoft monitors both IP and domain reputation, with increasing emphasis on the latter. A sudden increase in sending volume or a new sending IP can also raise red flags if not properly warmed up.
Ensuring the alignment of your SPF, DKIM, and DMARC records with your sending domain is fundamental. Here's an example of a simple DMARC record that you can find in your DNS records:
This record tells receiving servers your policy for handling emails that fail DMARC, and where to send reports. Properly set up authentication builds trust with Microsoft's filters. You can read more about Outlook's new sender requirements.
Content quality and recipient engagement
Even with perfect technical setup, your email content and recipient engagement can land you in the spam folder. Spam filters analyze email content for suspicious keywords, excessive links, or image-to-text ratios that might indicate spam. Generic subject lines or a lack of personalization can also contribute to lower engagement and higher spam complaints.
Low engagement rates, such as low open rates and click-throughs, signal to mailbox providers like Microsoft that your emails aren't valued by recipients. This can lead to your emails being filtered into the junk folder, even if direct spam complaints are not high. It's a subtle but significant factor in reputation building.
Managing your sending volume and list hygiene is also essential. Sending too many emails to disengaged users or stale lists can quickly deplete your sender reputation. Consider segmenting your audience and sending more targeted emails to engaged subscribers to maintain a healthy sender score.
Content and engagement best practices
Personalize emails: Address recipients by name and tailor content to their interests to boost engagement.
Monitor engagement: Track open rates, click-through rates, and unsubscribe rates for insights.
Clean your list regularly: Remove inactive subscribers and email addresses that bounce.
Avoid spam triggers: Steer clear of excessive capitalization, exclamation marks, and spammy phrases.
Advanced troubleshooting and Microsoft tools
To gain deeper insights into your sending reputation with Microsoft, it's highly recommended to utilize their Sender Network Data Services (SNDS) and Junk Mail Reporting Program (JMRP). SNDS provides data on your IP reputation and complaint rates, while JMRP offers direct feedback on user spam complaints.
Some senders also explore third-party certification programs to enhance their deliverability, such as Return Path's certification. While these programs can offer benefits like exemption from certain SMTP rate limits and improved inbox placement, they do not guarantee 100% inbox delivery, as Microsoft's filtering is dynamic and continually evolving.
If you've checked all the technical boxes and your emails are still landing in the junk folder, consider these common scenarios and solutions:
Common issues
Emails are getting delivered but are flagged as spam.
Low sender reputation: Your IP or domain has a poor history with Outlook's internal filters.
Poor email list quality: Sending to unengaged or old contacts increases spam complaints.
Content issues: Spammy words, excessive images, or too many links.
It’s important to stay proactive with monitoring and adapting your sending strategy. You can also submit delisting requests through the Office 365 Anti-Spam IP Delist Portal if you suspect your IP has been blocked.
Views from the trenches
Best practices
Implement a double opt-in process for all new subscribers to ensure list quality.
Regularly clean your email lists by removing inactive or unengaged subscribers.
Segment your audience and send targeted content to improve engagement metrics.
Personalize your emails and subject lines to increase relevance and open rates.
Monitor your sender reputation using Microsoft's SNDS and JMRP tools.
Common pitfalls
Ignoring low engagement rates, assuming delivery is sufficient.
Sending emails to purchased or old, unverified email lists.
Failing to implement or properly configure SPF, DKIM, and DMARC.
Using generic or spammy content that triggers filters.
Suddenly increasing email volume without proper IP warm-up.
Expert tips
If emails are landing in the spam folder, consider a temporary reduction in sending volume.
Focus on re-engaging your most active subscribers before expanding your reach.
Monitor Microsoft's specific reputation metrics, not just generic blocklist status.
Ensure your sending domain and IP have a consistent positive sending history.
Keep an eye on content-based filtering, not just technical authentication.
Marketer view
Marketer from Email Geeks says analyzing email headers is crucial to ensure full alignment of the sending domain with SPF, DKIM, and DMARC, as well as the Return-Path.
2021-11-01 - Email Geeks
Marketer view
Marketer from Email Geeks says it's important to check your reputation at Microsoft via SNDS because spam placement is heavily influenced by sender reputation and recipient engagement.
2021-11-02 - Email Geeks
Ensuring inbox delivery
Getting your emails into the inbox for Outlook and Hotmail addresses requires a multi-faceted approach. It's not just about avoiding blacklists, but also about building a strong sender reputation through proper technical configuration, engaging content, and diligent list management.
By understanding Microsoft's unique filtering mechanisms, regularly monitoring your sender health, and focusing on sending high-quality, relevant emails to an engaged audience, you can significantly improve your chances of landing in the inbox and not the junk folder.
Microsoft that your emails aren't valued by recipients. This can lead to your emails being filtered into the junk folder, even if direct spam complaints are not high. It's a subtle but significant factor in reputation building.
Outlook's internal filters.
Microsoft's Sender Support.
