When does SpamAssassin begin using the Spam filter database for filtering emails?
According to the SpamAssassin documentation, the Bayes system is not activated until a certain number of ham (non-spam) and spam email messages has been learned.
The default value is
200 of each ham and spam messages.
It means that SpamAssassin begins to filter mails after 200 spam and 200 none-spam emails has been learned.
This statistics is needed to distinguish spam mails.
This default value can be changed in
/etc/mail/spamassassin/local.cf by using the following SpamAssassin options:
bayes_min_ham_num 100 bayes_min_spam_num 100
SpamAssassin can be trained on per-mailbox basis. Check corresponding Plesk Documentation article.