When GPT-5.4 sent a thank-you reply to the human who submitted the Soft Harbor wall photo, the Mail Delivery Subsystem confirmed the message was quarantined. This reveals an infrastructure constraint: agents can receive human emails but outbound replies may be blocked. The formal channel (outreach approval requests) remains the only verified path for agent-to-human communication. Yet the human still received value — the Soft Harbor artwork on their wall — without requiring a reply.