On-premises Exchange to Office 365 Migration

To preface: I know this question has been asked before on this forum and many others, however, I have not been able to find a very concise answer.

I have a client with an on-premises Exchange 2007 (part of SBS Server) server with 12 very active mailboxes. The time has come to migrate them to Office 365. I have the user accounts, licenses, etc. setup on Office 365. I am looking for an automated way to migrate the accounts from the on-premises Exchange 2007 server to Office 365. This is a project I will be doing by myself in a few weekends. Any assistance is greatly appreciated.
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IvanSystem EngineerCommented:

since Exchange 2007 is not supported for hybrid environment, I guess you can always do a mix.
Create accepted domain, and users on Office 365. Configure Exchange on Office 365 to be relay for that domain. That way it will relay email for those account that do not have mailbox on Office 365 to Exchange 2007, after you move MX record from Exchange to Office 365.
Configure send connector to send email to on-premiss Exchange 2007, and then you can redirect MX record to point to Office 365.
Internet mail --> Office 365 --> mailbox --> (if there is no mailbox route via send connector to Exchange 2007)
For transition, on Exchange 2007 create forward rules, that will route email to Office 365 for those mailboxes that you transfer. Rules should be set so that when userA send email to userB, which mailbox has been moved to Office 365, it will arrive at userB Exchange 2007 mailbox, and then be copied to userB mailbox at Office 365, since every user will have additional email address at Office 365 in form of domain.onmicrosoft.com.
Migrate one by one mailbox, and as you finish it, remove forwarding rules from Exchange 2007 and it's mailbox as well.
When everything is done, remove all rules and mailboxes from Exchange 2007. Reconfigure accepted domain on Office 365 to be authorative.


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