As mentioned in the UTM feature
Add X-Spam-Flag Header with spam action "warn"
We would like an option in email scanning rules to add an x-spam-flag header to incoming emails that are possible spam. This would be alternative to the prepending *POSSIBLE SPAM* that it does currently.
The point of this is that many mail clients support checking for these x-spam headers in messages and can drop the emails into the junkmail folders where users can manage themselves outside of watching quarantine, and without the ugly subject modification currently used.