My interpretation is: Spam is deleted in order to give you plausible deniability that you haven't received and read it.
i.e. There is no spam folder.
But, this seems like it would normally be a bug rather than a feature.
Peer (mailbox.org)
It is not exactly clear (on the website) what you mean by 'rejected', so the English text could be improved to make your meaning more explicit. Perhaps 'returned' would be better?
Good luck!
That's a big and very important difference.
It's a good approach, and from a legal perspective I'm surprised more systems don't take this approach, because legally (at least in my local jurisdiction), you're deemed to have received an email when it "enters that information system" - i.e. when your SMTP server says 250.
This stuff matters quite a lot in the formation of contracts.
On reflection, this does seem like a better system. I had imagined a silent fail as per other popular e-mail hosts.
This is important, because the receiving system doesn't have a guaranteed way of reaching the sender - modern spam typically fakes the "From:" and <return-path> fields - so well-run systems nowadays never try to do so for fear of generating what's referred to as email backscatter spam.