This article explains why emails are not being forwarded to the Continuity Service and why attempts continue to deliver them to the destination server even though the service has been activated. This behavior can occur if the Continuity Service was activated only recently.
How Long Does It Take to Activate the Continuity Service?
The Continuity Service must be activated before the failure of your destination server. Please note that the initial activation can take up to four hours, as during this time the mailboxes and associated databases are created. Only then can you log in to the webmail client in the event of a mail server outage.
To activate the service, please follow this article: Activate the Continuity Service
After activating the Continuity Service, delayed emails are not retrospectively captured. The Continuity Service only accesses new emails that arrive after the service has been fully set up.
Emails already delayed will continue to be attempted for delivery to the destination server. If delivery is not possible within 24 hours, the delivery attempt will be permanently aborted, and the sender will receive a Non-Delivery Report (NDR) informing them of the failed delivery attempt.
If you want to learn why, despite successful setup and activation, an email is not forwarded from the Continuity Service to your destination server, please read the following article: