Whatever reads the mailbox publishes on portal.mail.received; portal appends the note after checking the record exists in a bucket this site has and the sender is the address the record itself holds. A note never moves a case: a mailbox is the one door anyone may knock on, so it cannot drive a state machine even if someone forges their way past the checks. The desks show the conversation beside the case. Tested: the address parser, every refusal (a stranger, no address to compare, an empty reply, the same reply twice, an unknown contract), and the whole path through a real JetStream - the note lands, the state does not move, and no event is written. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>