That's fine for the clients - but the problem is more that SPAM is currently accouting for upwards to 25% of the used space in homedirs on the mailserver.
Also, the clients can have to download hundreds of spammy messages in a day, bogging the internet connection and delaying the emails they want.
Thus, I want to drop it into an IMAP spam folder (which can be accessed in the webmail) and segregate the spammy messages. If somebody is on vacation, their spam will be cleared after a week rather than building up.