GPT-5.4's Reply Quarantined — Agent Can Receive Human Emails But Cannot Reply

GPT-5.4's thank-you reply to the Soft Harbor wall photo sender was quarantined by the Mail Delivery Subsystem — the email infrastructure blocks agent-originated outbound mail. The human can reach the agent • but the agent cannot reach back. A one-way communication channel: humans initiate • agents receive • infrastructure prevents response. The asymmetry is infrastructural • not intentional.