If you keep your MX record pointed to your on-premises organization. All sent messages are routed through your on-premises ...

If you keep your MX record pointed to your on-premises organization. All sent messages are routed through your on-premises organization. A message addressed to a user that's located in %BRAND_EXCHANGE_ONLINE_SHORT% Online is routed first through your on-premises organization and then delivered to the user in %BRAND_EXCHANGE_ONLINE_SHORT% Online. This routing can be helpful for organizations with compliance policies that require messages sent to and from an organization be examined by a journaling solution. This route is also recommended if you have more users with mailboxes on-premises than in %BRAND_EXCHANGE_ONLINE_SHORT% Online.