How to fix Outlook junk mail placement and high SCL scores despite proper email authentication?
Michael Ko
Co-founder & CEO, Suped
Published 3 Jun 2025
Updated 19 Aug 2025
9 min read
Dealing with email deliverability issues, particularly when messages land in the junk folder despite seemingly perfect email authentication, can be incredibly frustrating. I often encounter situations where a client's emails, fully authenticated with SPF, DKIM, and DMARC, still receive high Spam Confidence Level (SCL) scores from Outlook, leading to poor inbox placement. This behavior suggests that Microsoft's filtering systems are evaluating more than just the foundational authentication protocols. It points to a deeper assessment of overall sender reputation and content.
The challenge is that the solution isn't always straightforward. It's not just about passing authentication, which is table stakes for good deliverability. We need to look at a broader spectrum of factors that contribute to a sender's trustworthiness in the eyes of an email service provider like Microsoft Outlook. This includes understanding the nuances of their filtering systems and how various elements of your email campaigns are perceived.
When your emails are ending up in the junk mail folder, especially with a high SCL, it means Outlook's internal filters (Exchange Online Protection or EOP) have flagged them. An SCL of 5, for instance, indicates a moderate to high likelihood of spam, while an SCL of 9 is a strong indicator of spam. It is important to remember that this score is a crucial indicator within Outlook's own filtering mechanisms. You can read more about how Microsoft Exchange Online Protection works to get a deeper understanding.
It is also worth noting that beyond SCL, there's also the Bulk Confidence Level (BCL), which assesses if an email is bulk mail, and if that bulk mail is likely to be spam. A high BCL can also contribute to emails landing in junk, even if the content isn't explicitly spammy. You might find your emails getting a BCL of 5, which means some companies will still receive them in the inbox, but others with stricter policies might junk them.
While Microsofthas deprecated SmartScreen support in favor of EOP's more modern filtering stack, the core principle remains: a combination of factors beyond just basic authentication influences deliverability. This modern stack emphasizes IP and domain reputation, as well as campaign detection. This means your mail stream's overall perception is critical.
The header above, specifically SFV:SPM, indicates the message was marked as spam by Exchange Online Protection's spam filters. This means Outlook itself is the one making the judgment, potentially inheriting a broader negative perception of your sending practices.
Reputation is more than just authentication
Even with perfect SPF, DKIM, and DMARC records, your sender reputation can be negatively impacted by factors unrelated to these technical authentications. The overall mailstream reputation, encompassing everything from your sending IP and domain to user engagement and complaint rates, heavily influences Microsoft's filters.
A key issue is often the quality and permission level of your email list. If your recipients are not actively engaging with your emails, or worse, marking them as spam, this feedback signals to Outlook that your mail is unwanted. This can lead to your emails being directed to the junk folder, regardless of your authentication setup. To understand more, read our guide on why authenticated emails go to junk in Microsoft Outlook.
Similarly, a compromised domain or IP (i.e., being on a blocklist or blacklist) can immediately destroy your sender reputation, making it nearly impossible to reach the inbox. Even if your authentication is technically correct, if your IP or domain has a history of sending unwanted mail, filters will penalize you. Monitoring your sender reputation and checking for blocklist (or blacklist) presence is crucial, and you can learn more about it in our comprehensive article, A practical guide to understanding your email domain reputation.
Content and sender identity factors
My testing has shown that even subtle changes in email design or sender identity can dramatically alter Outlook's SCL scoring. For instance, sending HTML emails versus text-only emails can be a significant factor. HTML emails often contain more elements that spam filters might scrutinize, such as images, links, or specific formatting that can trigger higher SCL scores. Plain text emails, being simpler, often bypass these content-based filters more easily. If you send automated, templated emails, consider how their structure might impact your placement, as discussed in why automated templated emails land in Outlook junk.
The sender's email address and alias also play a role. Using generic addresses like 'noreply@yourdomain.com' sometimes results in better deliverability compared to personalized or less common aliases like 'daniel@yourdomain.com' or 'sender@yourdomain.com'. This could be because 'noreply' addresses are frequently associated with transactional or legitimate automated emails, which typically have higher engagement rates.
Finally, the dedicated IP address used for sending can profoundly impact your SCL. If an IP has a poor sending history, even if your domain authentication is solid, it can drag down your deliverability. This suggests that Outlook uses a blend of IP, domain, and content analysis to determine SCL, making a holistic approach essential for improving your MicrosoftSCL score on Outlook.
Strategies for improving placement and SCL scores
To improve Outlook junk mail placement and reduce high SCL scores, you need a multi-pronged strategy that goes beyond just email authentication. Here are some actionable steps I've found effective:
Audience segmentation: Ensure you're sending to engaged recipients. Regularly clean your email lists to remove inactive contacts, known spam traps, and invalid addresses. High bounce rates or low engagement can significantly hurt your sender reputation and lead to higher SCL scores.
Content optimization: Review your email content for elements that might trigger spam filters. This includes excessive links, spammy keywords, disproportionate image-to-text ratios, or hidden text. Test both HTML and plain text versions to see which performs better. Sometimes, a simpler, less graphically intensive email is more effective.
Sender identity consistency: Experiment with different 'From' names and email addresses. While 'noreply' can sometimes offer better deliverability, evaluate if a more recognizable, yet trusted, sender name could improve engagement and thus, reputation. Make sure your sender alias is professional and not overly promotional.
IP and domain reputation management:Continuously monitor your sending IP and domain reputation with Outlook's own tools or third-party monitoring services. If you suspect your IP or domain has been blocklisted (or blacklisted), investigate immediately to request delisting and address the root cause. This includes understanding the impact of what happens when your domain is on an email blacklist and how to recover.
Feedback loops and complaint rates: Register for Microsoft's Junk Mail Reporting Program if available. This provides you with data on when your recipients mark your emails as junk, allowing you to remove those users from your list promptly.
Remember, improving deliverability is an ongoing process. Consistent positive sending behavior over time is key to building a strong reputation with Internet Service Providers (ISPs), including Microsoft Outlook, and ensuring your messages reach the inbox.
Views from the trenches
Best practices
Maintain a clean email list by regularly removing inactive or unengaged subscribers to improve overall engagement metrics.
Segment your audience and tailor content to ensure relevance, reducing the likelihood of spam complaints and bounces.
Prioritize plain text or minimalist HTML emails for critical communications, as they tend to be less scrutinized by content filters.
Actively monitor your IP and domain reputation across major providers and address any blocklist (or blacklist) issues immediately.
Implement a double opt-in process for all new subscribers to ensure explicit consent and a high-quality mailing list.
Common pitfalls
Ignoring high SCL or BCL scores, assuming proper authentication is sufficient for inbox delivery.
Sending a high volume of emails to unengaged or old lists, which quickly degrades sender reputation.
Using overly promotional or spammy keywords and phrases in email subject lines or body content.
Failing to implement DMARC, or setting a policy of 'none', which leaves you vulnerable to domain spoofing.
Relying solely on a single dedicated IP without diversifying sending practices for different email types.
Expert tips
If you suspect an external filter is at play, check your email headers thoroughly for additional anti-spam report fields that might reveal the filtering source.
Consider engaging in a slow and steady IP warm-up process for new IPs or domains to build a positive reputation gradually.
Analyze your email content for elements that trigger SCL increases, such as excessive links, specific phrases, or image-to-text ratios.
Periodically send test emails to various Outlook and Office 365 accounts to observe deliverability and header information in real-time.
Collaborate with your IT or network team to identify any layered email security solutions that might be influencing inbound filtering for your domain.
Marketer view
Marketer from Email Geeks says they had a client experiencing Outlook junk mail issues with a reported SCL of 5, despite correct SPF, DKIM, and DMARC. They found that only text-only emails, using 'noreply' in the address, or changing the dedicated IP consistently landed in the inbox, suggesting strict filtering based on content and sender identity.
2019-10-30 - Email Geeks
Expert view
Expert from Email Geeks says that filters operate on the mailstream, and changes to email content, sender, or IP can distinguish mail enough to bypass existing filters. They believe the core problem is the overall mailstream reputation, not just IP or domain, due to recipients disliking the content.
2019-10-30 - Email Geeks
The holistic approach to email deliverability
Ultimately, fixing Outlook junk mail placement and high SCL scores is a nuanced process that demands attention to detail beyond just authenticating your emails. While SPF, DKIM, and DMARC are non-negotiable foundations for email security and deliverability, they are only one piece of the puzzle. Microsoft's sophisticated filtering, particularly Exchange Online Protection, considers a wide array of factors, from your sending IP and domain reputation to the subtle characteristics of your email content and sender identity.
The key is to understand that a high SCL often signals a broader issue with your email program's perception by recipients. This includes how clean your mailing lists are, how engaged your subscribers are, and whether your content or sending patterns mimic those of spammers. By proactively managing your sender reputation, optimizing your email content, maintaining a healthy sender list, and diligently monitoring deliverability metrics, you can significantly improve your inbox placement with Outlook and other major inbox providers.
Microsoft Outlook. This includes understanding the nuances of their filtering systems and how various elements of your email campaigns are perceived.
Continuously monitor your sending IP and domain reputation with Outlook's own tools or third-party monitoring services. If you suspect your IP or domain has been blocklisted (or blacklisted), investigate immediately to request delisting and address the root cause. This includes understanding the impact of what happens when your domain is on an email blacklist and how to recover.
