Looks like someone bought up a bunch of leaked iCloud email addresses and is sending spam out to us using ***.i.softbank.jp email addresses letting it pass the spam filters.
Just setup a rule on icloud.com to delete anything from that address.
I find apple email to be deficient in manging rules, spam filtering and overall controlling your email. I've largely been transitioning over to proton mail with my own domain. The flexibility and control is stark compared to apple mail. I'll still use my icloud email but just for apple stuff, i.e., apple products, and software I buy for my mac/iphone