Make certain you are on SmarterMail 14.4.5793.28950 - it's a special build and on the SmarterMail pages in the forums. You'll need that to handle SPF, DKIM and DMARC exceptions which were causing false positives and were fixed.
In my experience, use nothing except the SmarterMail antispam, setup per my document.
Do not allow users to override spam settings. Enforce Greylisting, and shut down all other antispam.
I will have it updated, to reflect additional spam from new domains, next week.
See: https://portal.chicagonettech.com/kb/a171/smartermail-antispam-settings-document.aspx
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