We are currently at the very early stages of migrating Office and mainly Exchange mailboxes to Office 365.
I have found one implementation guide that states you have to completely remove the on premise exchange server (Exchange Server 2003) from AD as a prerequisite before installing and configuring ADSYNC on a server but can't find this stated in any other guides.
Not sure how you would then move the mailboxes. I have already backed up Exchange and exported mailboxes to PST.
Does anyone know if this is correct? I only have about 30 mailboxes to move.