I use this for quite some time and it has proven to be effective.
How to train bayes and prevent even more spam:
Go to search and reports and create filter like this: Please adjust spam scores according to your setup.
Then go to "Message operations" and select spam mails you want to train.
Point of this doing is that you learn bayes, so that when such mail is send from legit but hacked account (DKIM and SPF pass), bayes would catch it anyway. I do this once a week and it takes cca 15 minutes of work and bayes is more effective this way

Maybe this helps someone
