spam confidence level (SCL)

Spam confidence level (SCL) is a numerical value indicating the likelihood that an incoming email message is spam. SCL is a component of the Microsoft Exchange spam filter, Intelligent Message Filter (Exchange IMF).

The Exchange IMF evaluates message headers, content and other components of incoming mail and assigns an SCL ranking between zero and nine. An SCL of nine identifies a message that is almost certainly spam and an SCL of zero a message that is highly unlikely to be spam.