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Same UPN suffice between forest trusts

    Question

  • Hi guys,

    Apologies but this may be more of an AD related question than an exchange one however we have a Exchange Hybrid setup (2013) with most of our staff accounts that have been migrated to Office 365. We have 2 domains configured with a full forest trust and need to add a 3rd domain.

    We initially setup a UPN which is in two of our domains, *its not the primary* however 17 users in one domain use the UPN to login to Office365 which is also their email address (their PC's aren't joined to the domain). The new domain will be called the same name as the UPN suffix and users will use this UPN as their primary exchange login and email address. Do you know if this will cause any issues?

    I haven't enabled the UPN suffix to traverse the forest yet to the new domain.

    Thanks for any replies :)

    Thursday, May 31, 2018 8:50 AM

All replies

  • Hi,

    For your question:
    The new domain will be called the same name as the UPN suffix and users will use this UPN as their primary exchange login and email address. Do you know if this will cause any issues?

    I'm afraid that the same UPN suffix cannot be shared among trusted forest. Below is a detailed explanation for this, which indicates that it will cause the logon authentication issues:

    Forest trust can't share same UPN Suffixes

    Hope it helps.

    Regards,

    Manu Meng


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    Friday, June 01, 2018 8:28 AM
    Moderator
  • Hi,

    Just checking in to see if above information was helpful. Please let us know if you would like further assistance.

    Regards,

    Manu Meng


    Please remember to mark the replies as answers if they helped. If you have feedback for TechNet Subscriber Support, contact tnsf@microsoft.com.

    Click here to learn more. Visit the dedicated forum to share, explore and talk to experts about Microsoft Teams.

    Wednesday, June 06, 2018 9:50 AM
    Moderator