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Spam Confidence Levels

Exchange 2013
 

Applies to: Exchange Online Protection, Exchange Online

Topic Last Modified: 2013-05-14

When an email message goes through spam filtering it is assigned a spam score. That score is mapped to an individual Spam Confidence Level (SCL) rating and stamped in an X-header. The service takes actions upon the messages depending upon the spam confidence interpretation of the SCL rating. The following table shows how the different SCL ratings are interpreted by the filters and the default action that is taken on inbound messages for each rating.

 

SCL Rating Spam Confidence Interpretation Default Action

-1

Non-spam coming from a safe sender, safe recipient, or safe listed IP address (trusted partner)

Deliver the message to the recipients’ inbox.

0, 1

Non-spam because the message was scanned and determined to be clean

Deliver the message to the recipients’ inbox.

5, 6

Spam

Deliver the message to the recipients’ Junk Email folder.

9

High confidence spam

Deliver the message to the recipients’ Junk Email folder.

tipTip:
SCL ratings of 2, 3, 4, 7, and 8 are not used by the service. An SCL rating of 5 or 6 is considered suspected spam, which is less certain to be spam than an SCL rating of 9, which is considered certain spam. Different actions for spam and high confidence spam can be configured via your content filter policies in the Exchange admin center. For more information, see Configure Content Filter Policies. You can also set the SCL rating for specific conditions using Transport rules; for more information about how to create a Transport rule, see Manage Transport Rules.

 
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