The Emergency Inbox feature allows you to continue to send and receive emails when your mail service (Microsoft 365, hosted Exchange server, etc.) is not responding. This could be the result of planned maintenance or an outage. While the mail service is unavailable, Proofpoint queues incoming email while also making it available within the Emergency Inbox. Users can access the Emergency Inbox to view and respond to incoming emails and create outgoing emails until normal service is restored. When the mail service resumes normal operations, emails sent or received during the outage are delivered to the mail server and the Emergency Inbox is emptied. 

The Emergency Inbox is automatically activated upon an outage. When the mail service is operating normally, the Emergency Inbox is empty.