Hybrid Exchange with O365 Bounce back for Cloud only mailboxes

Question

Hi All,

Currently, our exchange is in hybrid with O365, and what we've discovered is that if we create a cloud only mailbox, when an internal application/printer using our on-prem exchange as the smtp relay is sent to the cloud only mailbox, it gets bounced back because the user's mailbox doesn't exist on the on-prem exchange. To get around this we have to create the user's mailbox through the on-prem exchange console. However, we'd like to avoid creating exchange on-prem mailboxes, and just create cloud only accounts.  Is there a way we can get the exchange on-prem to relay mail to O365 without failing because the user's mailbox doesn't exists on the exchange on-prem. Ideally, going forward we'd like to create cloud only mailboxes due integrations we've implemented, and have the exchange on-prem just be the smtp realy to those accounts without checking if the mailbox exists on the exchange on-prem, until we can remove the hybrid. 

Any advice would be appreciated

Thanks

Answer 1

Hi, send the messages from the applications/printers to the mailbox's onmicrosoft.com email address instead.

The on-prem Exch Server will route through the hybrid connector to 365 since that email address wont exist on-prem.