How do I interpret SCL scores in Microsoft headers?
Summary
What email marketers say8Marketer opinions
Email marketer from Reddit shares that SCL values of 0-2 generally indicate that the message is considered 'good' or likely not spam. These messages have passed most spam checks.
Email marketer from Spamlaws.com explains that while SCL scores can help filter spam, it's important to ensure that legitimate emails are not mistakenly classified as spam. Overly aggressive spam filtering can have legal implications, particularly if it interferes with business communications or violates anti-discrimination laws.
Email marketer from Practical365 shares that organizations can configure Exchange to take specific actions based on SCL values. For example, messages with an SCL of 7 or higher might be automatically moved to the Junk Email folder, while messages with an SCL of 9 might be deleted.
Email marketer from MXToolbox explains that understanding SCL values allows administrators to create more effective spam filtering rules. By analyzing the SCL values of legitimate and spam emails, administrators can fine-tune their filtering thresholds to minimize false positives and false negatives.
Email marketer from EmailGeekForum shares that organizations can customize SCL thresholds to align with their specific needs and risk tolerance. For example, a financial institution might choose to use more aggressive spam filtering than a small business.
Email marketer from StackExchange explains that SCL values of 7 or higher strongly suggest that the message is spam and should be treated with caution. Messages with these scores often contain malicious content or phishing attempts.
Email marketer from TechTarget shares that several factors can influence SCL scores, including the sender's IP address reputation, the content of the message, and the presence of certain keywords or phrases commonly associated with spam.
Email marketer from EmailSecurityBlog explains that regularly monitoring SCL scores can help identify emerging spam trends and potential security threats. Sudden increases in SCL scores for certain types of messages may indicate a new phishing campaign or a vulnerability in your email infrastructure.
What the experts say3Expert opinions
Expert from Word to the Wise explains how Bayesian filtering systems can influence the SCL score by examining the content of the email and identifying patterns associated with spam.
Expert from Spam Resource explains that while SCL scores are a useful indicator, they should not be relied upon as the sole determinant of whether an email is spam. False positives and false negatives can occur, so it's important to consider other factors and use a multi-layered approach to spam filtering.
Expert from Email Geeks initially explains that any PCL (phishing confidence level) score is bad, then clarifies, after checking notes, that the SCL (spam confidence level) scale is 0-9, where 1-2 are low/neutral.
What the documentation says5Technical articles
Documentation from Microsoft Learn explains that SCL values are found within the message headers of an email. Specifically, the `X-MS-Exchange-Organization-SCL` header contains the SCL rating assigned by Exchange Online Protection (EOP).
Documentation from Cisco explains that Cisco Email Security Appliance (ESA) can integrate with Microsoft Exchange to utilize SCL values for enhanced spam detection and filtering. This integration allows ESA to leverage Exchange's spam filtering capabilities while providing additional layers of security.
Documentation from Proofpoint describes the difference between Spam Confidence Level (SCL) and Bulk Complaint Level (BCL) in email headers. SCL focuses on spam, BCL focuses on emails which aren't strictly spam but are marketing/bulk emails.
Documentation from Microsoft Learn explains that SCL values range from -1 to 9. -1 indicates that the message is not spam (e.g., from a safe sender or safe recipient), while values 0-9 represent increasing levels of spam probability. Higher values indicate a greater likelihood that a message is spam.
Documentation from Microsoft Learn describes various actions that can be taken based on SCL thresholds, including moving messages to the Junk Email folder, quarantining them, or rejecting them outright.