Below there is a chart of email processing on my server.
I process statistics every 5 minutes, So above image will tell you that i get about 4 real emails every 5 minutes. I have about 203 emails every 5 minutes that do not comply with email rules (invalid sender, SPF checks fail, etc) About 24 emails get rejected based on recipient rules (specific rules for one of my mailboxes).
And only 1 email every 5 minutes that would be accepted was recognised as spam. Considering the fact that i get multiple messages per day in my mailbox that should be considered as spam i decided that it is time to train spamassassin again.
Training SpamAssassin is quite easy aslong as you follow some rules and are willing to automate this task. As my server works with DirectAdmin I followed the Knowledge Base article on How to create a cronjob to use sa-learn to teach spamassassin – Maildir