Issue with User having mailbox on premise and in cloud RRS feed

  • Question

  • Hi

    we have a weird issue where we have a user with a mailbox on 2010 created in september with AD connect synced to office 365, the user is showing in portal.azure and in office 365 as synced with Active directory with a office 365 enterprise E3 license as she's using 2016 but it is showing she also has a mailbox in the cloud too.

    I don't see how this is possible and is causing an issue when anyone in the cloud sends her an email it gets sent to office365 mailbox and anyone locally is getting delivered to exchange 2010.

    please let me know how this can be resolved as I will need remove this online mailbox so she can receive all emails.

    Thank you.


    • Edited by mvaghji Wednesday, November 14, 2018 5:16 PM
    Wednesday, November 14, 2018 5:08 PM


  • Yes this can happen.  It's a sort of a race condition, for example when a mailbox is created for a user before the account is properly synchronized from AD.

    The general method is to:

    1.  Copy everything you want to keep from the cloud mailbox to a PST.

    2.  In AD, move the user account to an OU that is not synchronized to the cloud.

    3.  Start an Azure AD Connect sync or wait for the next one.

    4.  When the mailbox disappears from the online EAC, remove the user account from the recycle bin in MSOL PowerShell:

    Remove-MSOLUser -UserPrincipalName user@company.com -RemoveFromRecycleBin

    5.  In AD, move the user back to a synchronized OU.

    6.  Start an Azure AD Connect sync or wait for the next one.

    Now you can move the mailbox to Exchange Online or leave it where it is, but it should be properly configured in the cloud as an on-premises mailbox.  I'd recommend not applying an Exchange Online license if the user won't be needing one.

    Ed Crowley MVP "There are seldom good technological solutions to behavioral problems."
    Celebrating 20 years of providing Exchange peer support!

    • Proposed as answer by Niko.Cheng Thursday, November 15, 2018 8:52 AM
    • Marked as answer by mvaghji Thursday, November 15, 2018 4:54 PM
    Wednesday, November 14, 2018 5:28 PM