Parent has new Hosted Exchange domain, “parent.com”. We are “subsid.com”. We were advised to, and have, created new users in parent domain both AD and Exchange. That gives us access to both mailboxes in Outlook. Then have users move their created “subsid.com” folders to the new parent mailbox.
Then add the “subsid.com” domain to the O365 tenant and create “subsid.com” aliases for all the “parent.com” mail boxes.
When ready in O365 portal, change MX record for “subsid.com” to go to the O365 tenant for “parent.com”.
This way existing senders could send to the old “subsid.com” and mail would flow into the “parent.com” box. The idea here was to end up with one mailbox that would receive (and send) from either domain. We currently now have both mailboxes in place but many questions arise:
How do we handle shared mailboxes and resources, conferences rooms? How can we gracefully move our old Calendar events and meetings? Do these things all need to be recreated? That is our understanding with this method.
But, what about just migrating our existing domain, “subsid.com” into the O365 tenant and keeping everything as is? I know there are automated methods like "remote move" and a PS script. However, we have heard some bad horror stories about lots of errors, NDR's, Calendar events and meetings not working, etc...
Sorry to be so lengthy on this. I think that I favor the first method (new mailbox that can handle both domains). But our users are not happy and execs are not willing to have to redo all meetings and Calendar events and any other customizations. So, I need to consider the second "true migration" type method as well.
If you have a lot of experience with Hosted Exchange Migration I would love to hear your comments on this.
Thanks so much!