I am having the same problem after updating to 10.15.7. My symptoms:
- SpamSieve moves spam to my Spam folder (on the server) but only a few of them actually get colorized as spam.
- There seems to be a large increase in false positives, similar to what I see if SpamSieve operates with a brand new corpus.
- The Train As Good / Train As Spam menu options work as expected when trying to correct the mistakes caused by the above symptoms.
- Apple Mail and SpamSieve beachball for about 30 seconds on launch but otherwise seem to run normally after that.
I tried clicking on the link provided in this thread to set AppleMailPluginSetIsJunk=YES but after relaunching Apple Mail and SpamSieve the problem remains.
Is there anything else I should try? Thanks