Moving a mailbox from O365 to an on premises environment sounds like a complex task, but it is more simple than you might think it is. Here’s what you need to do:
Just once: Configure the migration endpoints in case your have multiple on prem exchange sites.
For each mailbox:
- In your on premises environment, create a mail enabled user (MEU) pointing to your O365 mailbox.
- Set the Mailbox GUID of the MEU to match the mailbox GUID of the O365 mailbox.
- Add the legacyexchangeDN as an X500 proxy address to both the MEU and the O365 mailbox.
- start the mailbox move from O365, using the migration endpoint that matches the destination site for the new on prem mailbox.