eM Client doesn’t have a spam detection ability. We leave that up to your email provider, so if they are not filtering your messages correctly that would be the place to start.
All eM Client has are Rules, including the Blacklist, that can move new messages from your Inbox to the Junk folder based on very specific information like the sender’s address or domain. If you setup a Rule, or add the sender’s address to the Blacklist, it will work only as long as they use that same address. But spammers avoid using the same address repeatedly because they are easily blocked that way. A Rule is not an effective way to manage spam. Better is to mark the message as spam in webmail for your email provider, and their server will learn from that, hopefully moving similar messages to spam in future.