My environment currently looks like this:
Office 365: mailboxes with primary addresses @subdomain.mydomain.com and secondary addresses @mydomain.com. These mailboxes were all created in Office 365 and not moved from on-premises.
On-premises: Exchange 2007 mailboxes with addresses @mydomain.com.
We have Forefront Identity Manager 2010 synchronizing Office 365 and on-premises so each has mail-enabled contacts for the mailboxes in the other. We have no other integration between Office 365 and on-premises (no hybrid, or ADFS).
Our goal is to move the mailboxes from Office 365 to the on-premises Exchange 2007 server. How do we do this?
As a side note, we are upgrading to Exchange 2013 on-premises soon so if we needed that we can use it.