Exchange Hybrid Wizard Federation Trust Domains

Mike00 236 Reputation points
2020-08-06T22:58:44.9+00:00

Hi,

I will be running the Hybrid Wizard to enable co-existence with Exchange Online. I have approximately 10 domains in Exchange on-premises and am wondering if I need to configure all of these when running through the Hybrid Wizard. What is the impact if only the primary email domain is selected instead of all of the domains. Currently only the primary domain has autodiscover setup as well so it is unlikely that the others will even work I am thinking?

Thanks,

Mike.

Exchange Server Management
Exchange Server Management
Exchange Server: A family of Microsoft client/server messaging and collaboration software.Management: The act or process of organizing, handling, directing or controlling something.
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Microsoft Exchange Hybrid Management
Microsoft Exchange Hybrid Management
Microsoft Exchange: Microsoft messaging and collaboration software.Hybrid Management: Organizing, handling, directing or controlling hybrid deployments.
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Accepted answer
  1. Andy David - MVP 140.8K Reputation points MVP
    2020-08-07T23:28:15.637+00:00

    Hi @Mike00 . Yes only the Primary SMTP domains should be selected. Why? Because that is what is used in autodiscover and in the org relationship between Exchange Online and on-prem ( Think Free/busy).
    The other accepted domains do not need to be selected in the Hybrid Wizard.

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  1. Andy David - MVP 140.8K Reputation points MVP
    2020-08-06T23:31:18.243+00:00

    You only need to to select the primary domain if that is the domain that is set for your users as their primary SMTP domain.
    The other domains can be accepted domains in 365 and on-prem but dont need a autodiscover record.

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  2. Mike00 236 Reputation points
    2020-08-07T00:03:11.717+00:00

    Thanks, some of the other domains are also used as PrimarySMTPAddresses. So in this scenario I am assuming that they will also need to be selected?

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  3. Lydia Zhou - MSFT 2,371 Reputation points Microsoft Employee
    2020-08-07T08:08:19.963+00:00

    How many domains you have verified in O365?
    If you still want to use those domain names for mailboxes in O365, you have to add all needed domains to O365. For your reference: Add a domain to Microsoft 365.