To switch on spam filtering for a mailbox:
If you receive lots of spam messages with the current setting, to make filter more sensitive, try setting a lesser value in the The score required before a mail is considered spam box; for example, 6.
If you are missing your e-mails because your spam filter thinks they are junk, try reducing filter sensitivity by setting a higher value in the The score required before a mail is considered spam box.
Note: To further improve spam filter accuracy, you may want to train your spam filter on e-mail messages you receive (see the instructions on improving accuracy of spam detection in the following section).