Bulk Complaint Level (BCL) & Spam Confidence Level (SCL) overview.

Marc 631 Reputation points
2021-06-20T16:03:40.17+00:00

I am trying to understand better one part of the EOP antispam setting especially what is behind the BCL system.
When we choose a number level for example 7 what is going to happen? All emails marked by Microsoft with 7 will be cosidered spam?
Where can I setup the SCL number value (from-1 to 9) ? I couldn't find this option in mail-flow > roule. Neither in Baypass spam filter.

Thanks

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Exchange Server Management
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  1. Andy David - MVP 142.7K Reputation points MVP
    2021-06-20T16:14:52.55+00:00

    365 determines the BCL level, you can adjust the settings to determine what happens to a message based on that BCL rating
    https://learn.microsoft.com/en-us/microsoft-365/security/office-365-security/bulk-complaint-level-values?view=o365-worldwide

    Microsoft uses both internal and third party sources to identify bulk mail and determine the appropriate BCL.

    107318-image.png

    As far as the SCL, you can use the anti-spam settings to set how a message is treated the same as the BCL:
    https://learn.microsoft.com/en-us/microsoft-365/security/office-365-security/configure-your-spam-filter-policies?view=o365-worldwide

    https://learn.microsoft.com/en-us/microsoft-365/security/office-365-security/spam-confidence-levels?view=o365-worldwide

    If you want to create a rule that sets a rule to allow messages and not apply anti-spam to them, follow:

    https://learn.microsoft.com/en-us/exchange/security-and-compliance/mail-flow-rules/use-rules-to-set-scl

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  2. Marc 631 Reputation points
    2021-06-20T19:35:10.067+00:00

    If I am right when we set the BCL to 7 all message we are going to receveive with a rate of 7,8,9 will be treated as spam the rest will pass.

    About SCL it is not clear where I can setup the "numerical" value. As per picture below I couldn't find this option.

    107364-bypass-spam-filtering.png

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  3. Andy David - MVP 142.7K Reputation points MVP
    2021-06-20T20:05:58.017+00:00

    BCL is not the quite the same as SCL.
    BCL is for bulk email that is considered Spammy or non -solicted.:
    https://learn.microsoft.com/en-us/microsoft-365/security/office-365-security/what-s-the-difference-between-junk-email-and-bulk-email?view=o365-worldwide

    Any bulk email that 356 tags as a 7 or above ( the default) will be treated depending on you have that set:
    On the Bulk email threshold & spam properties page that appears, configure the following settings:

    Bulk email threshold: Specifies the bulk complaint level (BCL) of a message that triggers the specified action for the Bulk spam filtering verdict that you configure on the next page (greater than the specified value, not greater than or equal to). A higher value indicates the message is less desirable (more likely to resemble spam). The default value is 7. For more information, see Bulk complaint level (BCL) in EOP and What's the difference between junk email and bulk email?.

    MarkAsSpamBulkMail is On: A BCL that's greater than the threshold is converted to an SCL 6 that corresponds to a filtering verdict of Spam, and the action for the Bulk filtering verdict is taken on the message.
    MarkAsSpamBulkMail is Off: The message is stamped with the BCL, but no action is taken for a Bulk filtering verdict. In effect, the BCL threshold and Bulk filtering verdict action are irrelevant.

    For the SCL transport rule, use that only if you want to bypass SCL scanning or set to another level:

    You are in the right spot in your picture

    107365-image.png

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  4. Marc 631 Reputation points
    2021-06-21T09:50:02.65+00:00

    Thank you againg AndyDavid.

    Just duble check with you.....MarkAsSpamBulkMail is for defoult On. When I setup the threshold for example on 5 it is converted to an SCL 6 that corresponds to Spam.
    All emails tagged with a number ugual or higher than 5 will be treated as spam. Am I right?


  5. Vincent Bolden 1 Reputation point
    2022-10-05T19:52:55.127+00:00

    Question is there any way to reset an SCL?

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