Settings -> Filters and Rules -> Spam Protection -> Advanced settings -> Custom

Ikea mass marketing emails are ~5.5 for me, and essentially all of the “false positives” in my spambox. The real spam is all 20+.

It looks like fastmail defaults the threshold to 5. Try increasing it to slightly above the score your legitimate emails get.

A bit off-topic, but I'm constantly surprised that e-mail companies are so bad at this. If I, as a user, keep corresponding with someone, what kind of brain-dead system keeps putting their mails to spam? (answer: gmail) I am communicating with them, do you really think they are spamming me? It's so frustrating. And yes, their SPF & similar headers are correct (or at least they seem to be, as G of course doesn't tell me why it went to spam). I know I can setup filters, but I thought they had that "smart" machine learning thingy? Or at least some simple "if" statements? /rant

To be fair, aliexpress is pretty spammy. If they use simple bayesian filter for their spam filter it's pretty understandable that aliexpress emails ended up being marked as spam.

To be fair, 70% of what I get from AliExpress is actually spam, despite having disabled all the email switches I could find. For each order, I get 3-5 near-useless emails and every visit to the site results in a week or two of "abandoned cart recovery" emails.