The special filtering mode for checking the work of rules and classification algorithm called testing mode. In that mode the filter is classifying all messages marked for training and displays the results in Log. The real training never happens in testing mode. The log items added during testing have a special prefix.

This mode is useful for checking how the filter recognizes the existing sets of messages. You can select one or more messages and mark them as non-spam from email client interface. You can mark as spam too, but if you have the option "Move messages marked as junk to the Junk folder" turned on, then some messages may suddenly be moved to Junk folder.

A special icon is displayed on the screen in testing mode. You can drag it to any place you wish.

You can set a shortcut for toggling testing mode in Shortcuts window.