The thing about any filter is that as the spammers test them, then they find ways to defeat them. I'm not going to duplicate the internet about how these work since that would be duplicating the web.
But most email services such as GMAIL and others do have a way to mark such as spam so it gets a look later or blocked. Some let you just block them as you encounter them.
Bob
How do spam filters work. Do they key on the address line, the subject line, something else?

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