The Dovecot antispam plugin watches a defined spam folder (defaults
to "SPAM"). It works together with a spam system that classifies
each message as it is delivered. When the message is classified as
spam, it shall be delivered to the spam folder, otherwise via the
regular filtering file the user may have (maildrop, Sieve, etc).
Now the user has everything classified as spam in the special spam
folder, everything else where it should be sorted to.
