As you may have noticed the RoundCube webmail system now has a button marked [Junk] (or [Roskaposti]). Please use this button if you encounter spam messages in your INBOX or any other folder where you receive mail. Its function is twofold: first it moves the message to your junk folder (Junk_E-mail), secondly it saves the message to be used as teaching material for SpamAssassin's Bayesian classifier. The classifier is re-trained daily based on your input.
If you open the junk folder you will notice that there is now a [Not junk] (or [Ei roskaposti]) button. It has the reverse effect: any erroneously classified message is returned to your INBOX, the SpamAssassin's markup is removed and the message is saved as a non-spam message to be used as training material.