Can spam protection work with greylisting turned off?

Hello everyone, new user here, I switched to mailbox from Gmail recently and so far I'm relatively satisfied except for the spam handling. I was a bit unhappy with Greylisting as it interfered with registering to new services; I always had to wait ~10 minutes for an email to arrive instead of it arriving instantly, so I tried turning Greylisting off. From the moment I did that, every single spam I receive goes right into my inbox.

Fortunately I don't receive that much spam, maybe 1-5 messages per day, but still. I move all the spam to the spam folder manually and I wait for the content spam filter to learn something, but it has been over a week and I have yet to see even a single spam message successfully recognized.

Am I doing something wrong? Does anyone have a better experience with the content spam filter? Is it because I mostly receive spam in Czech and the default content filter is maybe not trained on that?