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How to fix Outlook junk mail placement and high SCL scores despite proper email authentication?

Summary

Achieving optimal inbox placement in Outlook, especially when facing high SCL (Spam Confidence Level) scores despite having proper SPF, DKIM, and DMARC authentication, can be a complex challenge. This scenario often indicates deeper underlying issues beyond basic email authentication, pointing towards broader sender reputation or recipient engagement problems. Filters, including Microsoft's Exchange Online Protection (EOP) and potentially layered third-party solutions, analyze a mailstream holistically, not just individual authentication records.

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What email marketers say

Email marketers often find themselves grappling with the nuances of Outlook's spam filters, even when their emails appear to meet all technical authentication standards. Their experiences highlight that deliverability is a multi-faceted challenge, extending beyond simple SPF, DKIM, and DMARC passes. Marketers frequently point to the critical role of recipient engagement, list hygiene, and content quality, recognizing that even subtle changes can significantly influence inbox placement or lead to high SCL scores. They also underscore the importance of understanding specific error messages and adapting sending strategies to overcome persistent junking issues.

Marketer view

An email marketer from Email Geeks describes a perplexing Outlook junk mail issue, noting that despite perfect SPF, DKIM, and DMARC authentication, their client's emails consistently land in the junk folder with an SCL of 5. They highlight that achieving inbox placement is only possible under highly restrictive conditions. This includes sending text-only emails, using "noreply" in the email address, utilizing a different customer domain, or changing to another dedicated IP.

30 Oct 2019 - Email Geeks

Marketer view

An email marketer from Email Geeks explains receiving a specific message, "...marked as spam using a junk filter other than the Outlook Junk Email filter," when sending to domains using Outlook.com MX records. They interpret this as an indication that the email is being flagged by a filter external to, but inherited by, Office 365, leading to its junk placement.

30 Oct 2019 - Email Geeks

What the experts say

Deliverability experts often provide a deeper, more technical perspective on complex issues like high SCL scores despite proper authentication. They frequently emphasize that modern email filtering systems, including those used by Microsoft Outlook, operate on sophisticated algorithms that look beyond basic technical compliance. Their insights highlight the importance of holistic mailstream reputation, the nuanced impact of content and sender identity, and the potential for layered security solutions in large enterprise environments. Experts consistently point to recipient engagement and the quality of the mailing list as paramount factors in long-term inbox success.

Expert view

An email expert from Email Geeks explains that email filters operate based on the overall "mailstream" reputation. They clarify that the observed changes in email attributes (like text-only or specific sender addresses) merely make the emails distinct enough to temporarily bypass existing filters, rather than fundamentally resolving the underlying reputation issue.

30 Oct 2019 - Email Geeks

Expert view

An email expert from Email Geeks asserts that the primary issue lies with the overall mailstream reputation, not isolated to the IP or domain. They emphasize that the combined characteristics of the email campaigns are actively disliked by recipients, leading to consistent junking by filters.

30 Oct 2019 - Email Geeks

What the documentation says

Official documentation from Microsoft sheds light on the intricacies of their email filtering mechanisms, particularly Exchange Online Protection (EOP) and how it assigns SCL scores. These resources underscore that while proper email authentication is a baseline requirement, EOP's modern spam filtering stack relies heavily on a broader set of signals, including sending IP and domain reputation, as well as sophisticated campaign detection. The documentation clarifies how specific header values indicate the source of spam categorization and emphasize the need for senders to adhere to best practices beyond mere technical compliance to ensure optimal deliverability.

Technical article

Microsoft documentation on Exchange Server explains that the Spam Confidence Level (SCL) score is assigned to each message by the Content Filter agent, with higher scores indicating a greater likelihood of the message being spam. It states that the SCL threshold can be configured by administrators to determine the action taken on messages, such as moving them to the junk email folder, quarantine, or deleting them outright.

20 Jun 2024 - Microsoft Docs

Technical article

Microsoft documentation further details that an SCL score of 5 often indicates a "suspicious" message, frequently resulting in placement in the junk mail folder. It elaborates that this score is a crucial indicator for Exchange Online Protection (EOP) in assessing content-based spam likelihood and applying appropriate filtering actions, playing a vital role in email security.

20 Jun 2024 - Microsoft Docs

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