The analogy I’ve used for encryption with a backdoor is let’s say you wanted to store your valuables in someone eles safe, they give you a key to let you lock and unlock the safe as needed. If the owner of the safe has multiple keys to this safe how well do you think your stuff is safe from the owner?

Law enforcement is not the "good guys."

but if the backdoor is in the client device then having an encrypted mailbox doesn’t stop the snooping

Who is that ETC tla?

Now this feels like bad form of advertising. Like making scary ads to make people buy your product isnt really nice.