EMAIL ...Spam/Junk Mail Filter Levels
Stage 1. Server pre-checks often include Blacklists/Whitelists, SPF, DKIM
Stage 2. SpamAssassin on each mail account looks at many email properties
Stage 3. Client mail filters (ie Outlook/Thunderbird) ...moving good emails to the inbox trains the filter.
A. Step 2 to only mark and step 3 separate and filter more
B. Step 2 less strict and delete, Step 3 filter more.
C. Step 2 strict