The Emergency Inbox allows you to send and receive messages when your company’s mail systems are offline, either for planned maintenance or due to an unexpected outage. If the company mail systems stop receiving mail, the Emergency Inbox will automatically begin being populated with incoming messages. (It does not show messages that were successfully delivered prior to mail delivery being affected.) When the systems are functioning again, the Emergency Inbox will be cleared.
You can use the Emergency Inbox to send new messages as well as reply to received messages. Once email delivery has been restored any messages that were sent (both new and replies) are automatically delivered to your regular inbox.