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Blue Tongue
Asked: 2020-04-02 03:40:56 +0800 CST

O365 Hybrid: Can we select certain OUs and mailboxes to migrate instead of the whole forest?

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This is probably a dumb question to ask.

1) When we do the Azure Active Directory Connect to synchronise on-premises Active Directory, can we just select a particular OU which stores all active staff instead of the whole forest?

Apart from the user objects, I think other AD objects are synchronised as well.
Can we define which OUs to synchronise?

2) LIkewise, when we run Hybrid Config Wizard, can we just select to migrate a selected list of mailboxes but not all mailboxes?

Likewise for distribution groups, can we just select a certain number to migrate?

Thanks in advance.

exchange-hybrid

3 Answers

  1. You seem to be missing a key concept here: directory synchronization and Exchange hybrid configuration are not the same as the actual mailbox migration.

    In order to migrate mailboxes you need directory sync and an Exchange hybrid environment, but then you will decice which mailboxes will be migrated and when; it's perfectly fine to keep some mailboxes on-premises and some other ones online, even indefinitely.

    Regarding your questions:

    1) Yes, you can limit directory synchronization to specific OUs; but you should be very careful about that: if an object is not synchronized, all Office 365 services (including but not limited to Exchange Online) will not know anything about that object; this means, for example, that a non-synchronized user with an on-premises mailbox will not be known to Exchange Online; that can and will be a problem when on-premises and online users have to interact. Another example not related to Exchange: if you don't synchronize an user or a group, you will not be able to assign permissions to that user or group in any Office 365 service.

    2) The Hybrid Configuration wizard enables and configures the hybrid Exchange environment; it doesn't actually migrate anything.

    My advice is to synchronize everything, unless you are absolutely sure you don't need specific objects to be known to Office 365; excluding things from directory synchronization can bite you back later in unexpected ways.

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  2. When we do the Azure Active Directory Connect to synchronise on-premises Active Directory, can we just select a particular OU which stores all active staff instead of the whole forest?

    Yes. You can sync only selected OU's if you wish.

    Apart from the user objects, I think other AD objects are synchronised as well. Can we define which OUs to synchronise?

    Yes. You can sync only selected OU's if you wish.

    LIkewise, when we run Hybrid Config Wizard, can we just select to migrate a selected list of mailboxes but not all mailboxes?

    Yes. You can migrate only selected mailboxes if you wish.

    Likewise for distribution groups, can we just select a certain number to migrate?

    Yes. You can filter objects to prevent them from syncing to Office 365.

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  3. 1) Yes, you could do the following steps: 

    1.  Start the Azure AD Connect wizard
2.  Click Configure.
3.  Select Customize Synchronization Options and click Next.
4.  Enter your Azure AD credentials
5.  On the Connected Directories screen click Next.
6.  On the Domain and OU filtering page click Refresh.

    enter image description here https://docs.microsoft.com/en-us/azure/active-directory/hybrid/how-to-connect-sync-configure-filtering

    2) HCW just configure the hybrid deployment, it will not migrate mailboxes. You could select the mailboxes and migrate them in EAC, it just likes to move mailbox to another database.

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