Im about to do an Staged Migration from an Exchange 2007 to Office 365.
Im following this from Microsofts TechNet: http://technet.microsoft.com/en-us/library/jj874018(v=exchg.150).aspx
But in Best Practice in the bottum of page it says:
Inform users before you start the batch, because they'll stop receiving email sent to their on-premises mailboxes soon after the TargetAddress property is configured to forward mail to their Exchange Online mailbox.
Why does the On-Premises server stop receiving mail then i havent moved the MX record?
I trought I could create all the users and then sync all the email, test if it works on Office 365, move the MX and then make a final sync.