Forum Discussion
Exchange Online mail flow - forward emails with no mailbox to external receiver
You have two options for that scenario. First one is leave the MX pointing to on-premises and configure the domain as "internal relay" in O365. That way, Exchange Online will check for the presence of specific email address against the ExO GAL and if no match is found, will route it to where the MX record points at.
Alternatively, you can create a connector to route messages sent to specific recipients, either on a (sub)domain basis or by using a Transport rule. Check the documentation here: https://technet.microsoft.com/en-us/library/dn751020(v=exchg.150).aspx
You have two options for that scenario. First one is leave the MX pointing to on-premises and configure the domain as "internal relay" in O365. That way, Exchange Online will check for the presence of specific email address against the ExO GAL and if no match is found, will route it to where the MX record points at.
Alternatively, you can create a connector to route messages sent to specific recipients, either on a (sub)domain basis or by using a Transport rule. Check the documentation here: https://technet.microsoft.com/en-us/library/dn751020(v=exchg.150).aspx