Change AD Connect synced accounts to Exchange Online

Cap Sam 1 Reputation point
2022-03-19T10:28:48.357+00:00

Hello

We are using AD Connect to sync our on-premises AD to Azure AD.
We also have an Exchange on-premises server so mailboxes are not currently in the cloud. It is not yet set up in full hybrid mode.

We have had an outage to the onsite infrastructure which may take some time to resolve.

I have been asked about the possibility of enabling online mailboxes in O365 for some or all of the users. As the business is heavily reliant on email this would allow staff to at least use email in the meantime. We would then need to look at importing existing email from the onsite Exchange server when the connectivity is restored. It's not something I really want to do but I need to check if it's possible.

Is this something that can be done without causing more problems later on, apart from the obviously major hassle of exporting and importing mailboxes later ?

If it can be done what would be the process ? I assume AD Connect would need to be disabled but I don't know what steps we'd need to follow to do this correctly, enable the online mailboxes, then re-enable AD Connect later (when connectivity is restored) without creating inconsistencies in accounts.

Thanks

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7 answers

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  1. KyleXu-MSFT 26,211 Reputation points
    2022-03-21T01:45:18.317+00:00

    @Cap Sam

    It is suggested to use AAD connect and assign license to synced AD account for enabling Exchange online mailbox for that account.

    But, it is suggested to let Exchange online mailbox use the Exchange online default domain (user@Onlinedomain.onmicrosoft.com) as email address. If you use the local domain name as an email address, there will exist a conflict when Exchange on-premises run again.

    There will also exist a SPF issue if you use the local domain name as Exchange online mailbox email address without hybrid.

    After Exchange on-premises back to running, you could delete the Exchange online mailbox, keep using Exchange on-premises mailbox, migrate it to Exchange online later. Or you could delete Exchange on-premises mailbox, then change Exchange online mailbox from "user@Onlinedomain.onmicrosoft.com" to "user@localdomain.com" after creating hybrid.

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  2. Carlos Solís Salazar 16,611 Reputation points
    2022-03-19T21:45:22.687+00:00

    Hi @Cap Sam

    The only requirement to create an email from scratch is that your users have licenses of Exchange online (Plan 1 or Plan 2)

    the recommendation of @Thameur-BOURBITA and I will help you to migrate the email, after you recover your on-premises Email server.

    Hope this helps,
    Carlos Solís Salazar

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    179759-accept.png and 179670-upvote.png if any of the above helped so that, it can help others in the community looking for remediation for similar issues.

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  3. Cap Sam 1 Reputation point
    2022-03-19T14:41:05.62+00:00

    Hi

    So from the answers so far it seems this is something that can be done. But I was hoping there might be an existing step by step process to do this if someone has done this previously.

    I don't know what steps we need to follow to ensure we know how to do it and also so we don't create further problems.

    Thanks

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  4. Thameur-BOURBITA 32,586 Reputation points
    2022-03-19T11:30:51.1+00:00

    My question was - can we enable user mailboxes for online use without creating unfixable problems later on and, if so, how do we do this ?

    Sorry for the misunderstood , before answer to this question , you have to define which authentication method you will want to use to access on Exchange online?

    If you want keep your local Active directory the unique provider for authentication for all resource in could and local because you have already applied policies like password policy , in this case you should deploy Azure AD connect to ensure the synchronization and Single -Singn- On.

    Please don't forget to mark helpful reply as answer

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  5. Carlos Solís Salazar 16,611 Reputation points
    2022-03-19T11:21:42.507+00:00

    Hi @Cap Sam

    Thank you for asking this question on the **Microsoft Q&A Platform. **

    Short answer, yes you can create the mailbox in Exchange Online,

    You should keep running the Azure AD Connect, you still have some mail properties in the Domain Controller.

    After you recover your on-premises server, the effortless way is migrating the old mails via import PST

    Good luck.

    Hope this helps,
    Carlos Solís Salazar

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    Please 179759-accept.png and 179670-upvote.png if any of the above helped so that, it can help others in the community looking for remediation for similar issues.

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