I’m certainly no expert on the subtle heuristics involved in spam identification. But surely if, for the last few months, I receive a dozen emails per day with the content “Here are your banks documents.” and I mark each and every one of them as spam, gmail would get the idea that it’s probably spam.

At the very least the spammers should be grammatically correct. I have no idea if they mean “my bank’s documents”, “my banks’ documents” or “my banks, documents”. Perhaps I should just open the zip attachment and be done with it!