Hello Experts. In our env we have Exchange 2013 CU19 enterprise, with AD2012 R2. we are looking into migrating email to O365. we have multiple companies under us, all in one domain forest, with more then 30 accepted domains in on-prem exchange. We would like all mailflow to go through our on-prem environment. I'm looking through the connectors available in O365, and for inbound to O365 connector, i see the attached message. this seems to be only the case for emails coming inbound to o365 from our on-prem servers. It will be difficult for us to add all of our domains to O365 before we migrate any user since we have so many. our plan was to add domains one by one into O365 as we migrate that domains users aswell to O365.
but it sounds as though, then any emails that are sent from other on-prem domains that are not added to O365, that mail will fail to be delivered to the O365 migrated user. is there any way of getting around this limitation. I guess one thing we can do is to point the mx record to O365 as well for the domains whose users will be in O365, and remove that domain from the accepted domain from on-prem exchange, create a connector in O365 to accept emails from the internet. but with this, will the Free/Busy still function and will we still have the unified GAL between on-prem exchange and O365 users? And will we still be able to manage the user exchange accounts from on-prem exchange server?
Please let me know. Thanks in advance