i don't know what thunderbird thinks "sort by relevance" means for email searches but putting a message from my spam folder as the first result indicates it's very different from my definition of "sort by relevance"
@chr Search for a subject of "affinity product keys" or "affinity order confirmation" (which I found by the much-better email search in macOS mail, specifically with a search for "affinity serif")
unsolicited email client ramble
So now I use KMail, which tbh is about the same level of mess that Thunderbird is, but at least it has the features I want.
@chr In search results, "relevance" generally means how closely it matches your query.
i.e. how often similar words occur in that document.
Though true, it'd make sense to incorporate other factors in this determination. Sounds like they didn't think it through enough.