Currently running a hybrid Exchange 2013 environment, with DirSync and ADFS SSO.

We were looking to decommission all Exchange 2013 servers, but as we only have one, following some reading, MS state that one server has to remain if using DirSync and ADFS. Bang goes that idea.

Just to clarify the order of steps to take, for moving all mailboxes/groups to Office 365;

- Disable DirSync

- Remove any users from Office 365, whose mailboxes haven't been migrated already (at present, all staff have been provisioned in Office 365)

- Purge staff from Office 365 recycle bin

- Create staff migration batch in Exchange

- Convert on-premises mailboxes to MEUs, as per https://mikecrowley.wordpress.com/2010/12/09/converting-a-mailbox-to-a-mailuser-and-not-loosing-attributes/

(Has anyone tried these steps with Exchange 2013?)

- Re-enable DirSync

- Sort MX DNS record to point to O365 how long should we wait before doing this?

If there are any steps that I havent thought of, could anyone make any suggestions?

Many thanks.

It's my understanding that if you want to re-establish DirSync after having broken it (or never having established it in the first place) you're in for a lot of work.  If I were you, I'd leave DirSync and hybrid in place if I had any thoughts at all about returning to on-premises Exchange from the cloud at any point in the future.  This may be easier to deal with in future versions of DirSync or its successors, but I have no information on what's to come.

Hi,

We dont need to break down the DirSync during the mailbox migration. Please refer to the following article do a Cutover Exchange migration from Exchange 2013 to Exchange Online in your Hybrid environment:

https://technet.microsoft.com/en-us/library/jj874016(v=exchg.150).aspx

After a period of time that all of their mailboxes have been moved to Exchange Online, we can decommission your on-premises Exchange servers in a hybrid deployment. If you want to keep Active Directory Federation Services (AD FS) for user authentication of my Exchange Online mailboxes, please read the steps in Scenario Two of the following article:

https://technet.microsoft.com/en-us/library/dn931280(v=exchg.150).aspx

Regards,

As our Exchange server was still required for ADFS SSO and DirSync, we simply moved the mailboxes to the cloud, and opted out of a cutover scenario. Many thanks for the replies.

• Marked as answer by MR JH 17 hours 15 minutes ago