That's an interesting take about past/passed. Granted, I'm not really in a position to make good judgement calls about the English language either, but in my opinion it goes like this:
"passed" is something that happens or happened to you, like on the freeway you can say you have been passed by another vehicle.
"past", on the other hand, in this context is a state that refers to your location. Like in, "I'm past the red line". When you have to get past something, your position in relation to that something is expressed by that word.
Intuitively, I'd say that if it's the answer to an imaginary question of "where", it needs to be "past". If it's the answer to another question, like "what happened", it's "passed".
> I appreciate that the which/that distinction is tricky, but one is a restrictive clause and the other is not, changing the meaning of the sentence.
You're right, but I think we have to take non-native speakers into account. Also, the implication that those were the exact same emails doesn't really change with that, it only gets weaker. In my experience, people use that in the same way express a definitive relation. As in "those are the cats that ate the cheeseburgers" I get the impression that a specific set of cats are involved in a specific cheeseburger incident. That doesn't really change if you say "those are the cats who ate the cheeseburgers".
"passed" is something that happens or happened to you, like on the freeway you can say you have been passed by another vehicle.
"past", on the other hand, in this context is a state that refers to your location. Like in, "I'm past the red line". When you have to get past something, your position in relation to that something is expressed by that word.
Intuitively, I'd say that if it's the answer to an imaginary question of "where", it needs to be "past". If it's the answer to another question, like "what happened", it's "passed".
> I appreciate that the which/that distinction is tricky, but one is a restrictive clause and the other is not, changing the meaning of the sentence.
You're right, but I think we have to take non-native speakers into account. Also, the implication that those were the exact same emails doesn't really change with that, it only gets weaker. In my experience, people use that in the same way express a definitive relation. As in "those are the cats that ate the cheeseburgers" I get the impression that a specific set of cats are involved in a specific cheeseburger incident. That doesn't really change if you say "those are the cats who ate the cheeseburgers".