Your definition of "courier" is personal to you, but not compatible with anything that might be accepted by a judge.
In this case, Tile sent the email, it was delivered seamlessly to the plaintiffs' designated agents, and then it was hidden from the plaintiffs by their designated agents. Those agents are not couriers; as far as the law is concerned, and as far as the law can be concerned, they are the plaintiffs.
Tile has no control over who you make responsible for receiving your mail. As soon as they've gotten your mail to that person, they've done everything that can be done.
Which goes right back to what OP was saying, it's not taking into account how email actually works. The user did not mark it as spam, contrary to what you said earlier - they never even saw it. It's not even close to the same thing as the recipient tossing physical mail into the trash without opening it.
