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Donald Jacobs's avatar
Donald Jacobs
Copper Contributor
Nov 01, 2017

exchange hybrid multiple forests single email domain

Our county has a Single Exchange 2013 on-premise email server.  We provide email for 4 different Forest/Domains using linked accounts and AAD Connect to a single O365 tenant for G1/G3 licenses.  All users in all domains use the same email domain address.  hawaiicounty.gov.    I want to enable Exchange Hybrid but I'm not sure of what impact that will have for all forest/domains.   Any suggestions or documents on how to set up an Exchange Hybrid for this scenario is greatly appreciated.

hybrid
  • Joe Stocker's avatar
    Joe Stocker
    Bronze Contributor
    Nov 01, 2017

    The good news is it sounds like you have already done the hard part, which is getting AAD Connect to sync all objects from 4 different Forest/Domains to a single O365 tenant.

    Establishing Hybrid is simple in your case because you only have a single Exchange on-premises server.

    If you had a separate Exchange Server in each forest it would have been more complex.

    The Exchange Hybrid wizard in your case will be mostly the same as if you had a single forest with a single Exchange server because you have already done the hard part of doing the Identity sync with AAD Connect.

    So my advice is to follow the Exchange Deployment Assistant here:

    https://technet.microsoft.com/en-us/office/dn756393.aspx

     

    I assume that your AAD Connect was setup with this supported topology document in mind:

    https://docs.microsoft.com/en-us/azure/active-directory/connect/active-directory-aadconnect-topologies

     

    Review Hybrid Prerequisites here:

    https://technet.microsoft.com/en-us/library/hh534377(v=exchg.150).aspx

     

    One thing that you may run into that is not well documented anywhere is creating new accounts in those separate AD forests after hybrid is established. You'll need to create them as you normally would, then migrate those mailboxes to O365. Therefore, this requires you to maintain your Exchange Hybrid server until Microsoft resolves that issue (During the Ignite conference MSFT announced a future feature that will improve this scenario). Currently, there doesn't seem to be any way to create a linked mailbox directly in O365. For example, new-remotemailbox or enable-remotemailbox doesn't seem to support a linked mailbox scenario.

    Feel free to reach out to me directly if you need additional guidance:   joe@patriotconsultingtech.com

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