I have a hybrid Exchange deployment between on-premise Exchange 2010 (SP3) and Office 365. I am able to successfully migrate on-premise users to the cloud, and everything works correctly.
However, if I create a new AD user, sync it via DirSync and activate it on the cloud, the on-premise Exchange will completely ignore it. It will not appear in the GAL, and Exchange will even be unable to deliver mail to it.
Thus far, the only way I've found to make this work is to create an on-premise Exchange mailbox for the new user and then migrate that mailbox to the cloud; but this process is cumberstome and basically stupid, and I sincerely hope there is a better way to handle it.
What is the proper way to handle the creation of new users in a hybrid Exchange deployment?