Several post in this forum have asked for a community-based spam filtering system.   I am a skeptic of the idea, but nonetheless I was intrigued to discover that SonicWall has that feature.  Of all the on-premises spam filters that I have reviewed, SonicWall seems the closest to what I would like, although that judgement is based only on what I read in their online documentation

Apparently their Grid Network is only used for IP filtering, which is limiting, since so much spam comes from email service providers like Sendgrid and ExactTarget.   Here is a line from their website: (https://www.sonicwall.com/support/knowledge-base/email-security-connection-management-miscellaneous-options/170504630920103)