I’ve had SpamSieve installed for months, and it has been working as advertised. Rarely a mistake in sorting spam, and never after I’ve trained it on particular messages. Suddenly a few weeks ago it basically stopped working. Now 90% or more of spam goes into Apple’s “Junk” folder, and it’s often sorted incorrectly. Messages from one particular sender who is in my address book and whitelisted in SpamSieve go to Junk no matter what I do.
Nothing changed on this end. SpamSieve is set up as it always has been. I checked the spam filters on my mail service (Yahoo/ATT) and made sure that no filtering is happening at that level.
I have OS 10.11.5 installed, and SpamSieve 2.9.24. Mail has no rules operating except the one sends everything to SpamSieve.