Email management and security are crucial in today's digital communication. Outlook, a popular email client, employs various mechanisms to filter and categorize emails, ensuring users receive relevant and safe content. This article delves into three key triggers Outlook uses for email categorization: Bulk Complaint Level (BCL), Phishing Confidence Level (PCL), and Spam Confidence Level (SCL).
1. Bulk Complaint Level (BCL)
What is BCL?
Outlook assigns a Bulk Complaint Level (BCL) to emails from bulk senders. This level is determined based on the number of complaints Outlook receives from recipients about these emails. The BCL score ranges from 0 to 9, with a higher score indicating a greater likelihood of the email being spam.
BCL Values and Their Meanings
BCL value | Description |
0 | The message isn't from a bulk sender. |
1, 2, 3 | The message is from a bulk sender that generates few complaints. |
4, 5, 6, 7 | The message is from a bulk sender that generates a mixed number of complaints. |
8, 9 | The message is from a bulk sender that generates a high number of complaints. |
0: The message is not from a bulk sender.
1, 2, 3: Few complaints; the sender is likely reputable.
4, 5, 6, 7: Mixed number of complaints; potential for spam increases.
8, 9: High number of complaints; high likelihood of spam.
Emails with a BCL value from 4 to 9 are more likely to be marked as spam.
Good vs Bad Bulk Senders
Good bulk senders typically send desired and relevant content, resulting in fewer complaints. In contrast, some bulk senders distribute unsolicited messages resembling spam, leading to a higher number of complaints.
Reasons for High BCL
Emails marked as spam by users.
Similar content was previously marked as spam.
Recipients are not interested in the content.
Resolving High BCL Issues
Pause automated email campaigns.
Revise or create new email templates.
Ensure your contact list consists of interested subscribers.
Update templates in email management tools like Folderly.
Resume campaigns with improved content.
2. Phishing Confidence Level (PCL)
Understanding PCL
PCL is a measure used by Outlook to assess the likelihood of an email being a phishing attempt. It ranges from 1 to 8, with higher values indicating a higher probability of phishing.
PCL Values and Implications
PCL value | Verdict | Description |
1 through 3 | Neutral - email will be landed in Inbox folder | The message content isn't likely to be phishing. |
4 through 8 | Suspicious - email will be landed in Junk folder | The message content is likely to be phishing. |
1 through 3: Neutral; emails land in the Inbox.
4 through 8: Suspicious; likely to be phishing and land in the Junk folder.
Categories of Phishing Triggers
DIMP: Domain impersonation.
GIMP: Mailbox intelligence impersonation.
HPHSH/HPHISH: High confidence phishing.
INTOS: Intra-Organization phishing.
MALW: Malware.
SPOOF: Spoofing.
UIMP: User impersonation.
The reasons and resolutions for high PCL are similar to those in Gmail’s phishing triggers.
3. Spam Confidence Level (SCL)
What is SCL?
Inbound messages go through spam filtering in Outlook and are assigned a spam score. That score is mapped to an individual spam confidence level (SCL). A higher SCL value indicates a message is more likely to be spam.
SCL Values and Actions
SCL value | Description | Default action |
-1 | The message skipped spam filtering. For example, the message is from a safe sender, was sent to a safe recipient, or is from an email source server on the IP Allow List. For more information, see Create safe sender lists in EOP. | Deliver the message to recipient Inbox folders. |
0,1 | Spam filtering determined the message wasn't spam. | Deliver the message to recipient Inbox folders. |
5,6 | Spam filtering marked the message as Spam | Deliver the message to recipient Junk Email folders.
Strict preset security policy: Quarantine the message.
|
8, 9 | Spam filtering marked the message as High confidence spam | Deliver the message to recipient Junk Email folders.
Strict preset security policy: Quarantine the message.
|
-1: Skips spam filtering (e.g., safe senders).
0,1: Not spam; delivered to the Inbox.
5,6: Marked as spam; delivered to the Junk Email folder or quarantined.
8, 9: High confidence spam; similar actions as 5 and 6.
Emails with an SCL value of 5, 6, 8, or 9 are typically marked as spam.
Resolving High SCL Issues
The approach to resolving high SCL issues is similar to the strategies used for Gmail’s “Similar to messages that were identified as spam in the past” trigger.
Conclusion
Outlook's sophisticated email filtering mechanisms, including BCL, PCL, and SCL, play a vital role in protecting users from unwanted and potentially harmful content. Understanding these triggers and how to manage them is essential for anyone looking to maintain effective and safe email communication. By adhering to best practices in email management and content creation, senders can ensure their messages reach their intended audience without being flagged as spam or phishing attempts.