Retrain Apple Mail's built-in Junk Mail filters

Recently, Apple’s Mail program has started flagging legitimate mail as Junk, including mail from Apple News (how ironic, Apple flagging mail from!) and even mail I cc: to myself (the same address it was sent from!).

It’s still good at correctly catching junk, but I’ve been using Apple Mail for many years and this over-enthusiastic filtering behavior just started.

Is it possible to whitelist addresses?

Have you figured anything out with the Junk Filtering? It is even taking email from starred contacts and putting them in the Junk Mail folder. I have spent time on the phone with Apple Tech Support, which wasn’t any help. The Mail Preferences for Junk don’t seem to be followed by the app. I hate to start my days by looking in the Junk Mail Folder. Any suggestions would be welcome.

I think I might be able to improve things by disabling Apple’s junk-mail filtering completely and then re-enabling it as Apple claims this removes all training data and allows you to start retraining from scratch. But this isn’t optimal.