Persistent spam

I’m a longtime SpamSieve user and have been ever-so-pleased with the application since the day I bought it. It’s always served me extremely well. Within the last week or three I started persistent email from a source(s) that uses common wording, subject line, formatting and / or sender name. I’ve marked many messages as spam but the messages continue getting through. I suspect this is a setting I need to correct. Can anyone offer insight what I may have configured incorrectly? Thanks!

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