Hi - We're about to start a migration project from one on-prem exchange server to exchange online. Our outside contractor has decided that "hybrid-mode" was the path to go, so for many months we're going to have users on the on-prem server and in "the cloud". We currently receive mail for only one domain, and have only one on-prem server, so the SMTP route is pretty simple - one entry for "receiving domain" -> one "destination hosts".
Ok, on to the question: Once we enable hybrid-mode, the outside contractor says that mail can only be delivered to one of the two hosts (on-prem or in-cloud). Example: let's say my mailbox has been moved to the cloud. Incoming mail for me would hit the ESA and route to on-prem exchange and then route to the in-cloud mailbox. He states once we hit about 50% of mailboxes moved, we'll flip it and route all mail to the cloud and opposite would be true for someone that hasn't had their mailbox moved yet: incoming mail would hit the ESA and route to in-cloud exchange and then route to the on-prem mailbox.
While that seems like it would work, it seems highly inefficient considering we'll be in hybrid-mode for quite a few months. Is there a way both routes (on-prem and in-cloud) can be active at the same time and the ESA does a lookup to find out where the mailbox is? LDAP maybe?
thanks.
