obstinate spam

I am using a spam filter ( spameater pro) an an email client (becky!)
after I check my email with my spam filter,( for argument sake it shows 1 email,no spam), I open my email client and get a dozen or so spam emails and my email. Why ???, should the spameater have filtered all the emails, why does it say no mail left on server ? and yet I still receive spam emails with my client. I find that very frustrating. Has anyone experienced this odd behaviour ? and what can be done about it ?