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We use Exchange Online (O365) in our organization.

There is a quite huge mailbox (thee digit GB) in our tenant which belogs to an AD object we shall call user A. For reasons which are hard to explain and IMHO don't matter here, we will have to deleted the user A AD object and want user B to become the owner of this mailbox.

I was told this wasn't possible or we would have to bring that mailbox back on-premise first (a bit hard, given its size), perform the user change there, then migrate it again to the cloud.

Could someone explain why this seems to be so difficult / complicated to do it straight in the cloud?

Looking at my AD, I would assume that the attribute "Mailbox GUID" is what ties the mailbox to an AD object. Why can't I just delete that attribute on user A in our AD and add it to user B?

TorstenS
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  • An Exchange mailbox is always directly connected to an user account; it can't be (easily) remapped to a different one. – Massimo Feb 07 '21 at 18:24

2 Answers2

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You were told correctly. It can't be done.

Here are four ways you can accomplish what you need:

  1. Disable the user account for UserA. Grant UserB Full Access to the mailbox for UserA.

  2. Convert the mailbox for UserA to a Shared mailbox. Grant UserB Full Access to the mailbox for UserA.

  3. Export the contents of the mailbox of UserA to a PST file. Import the PST file into the mailbox of UserB.

  4. Export the contents of the mailbox of UserA to a PST file. Attach the PST file to the email client of UserB.

joeqwerty
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  • @joequerty I understand that these are not 4 steps to success but 4 alternative way to achieve what I am looking for, right? If I go for option 1., this sounds exactly what I was asking for. But in what tool would I "disable the user account for User A"? In AD or in Exchange? What exactly you mean by "disable"? Set "Account active" to false in AD? – TorstenS Feb 07 '21 at 17:26
  • For option 1, access the user account properties in on premises AD, go to the Account tab, check the box for "Account is disabled". Initiate a delta sync for Azure AD Connect, then log into the Office 365 Admin Center and navigate to the Exchange Admin center, then find the UserA mailbox and select it, then click the link to convert it to a shared mailbox, then access the UserA mailbox properties and select mailbox delegation, then grant users the Full Access permission for the mailbox. – joeqwerty Feb 07 '21 at 18:27
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Agree with joeqwerty. Which method you use depends on your actual needs. If you just need the content of user A, option 3 or 4 is better.

You also could refer to : Remove or Delete a former employee https://docs.microsoft.com/en-us/microsoft-365/admin/add-users/remove-former-employee?view=o365-worldwide

please note: OVERVIEW OF ALL THE STEPS TO REMOVE AN EMPLOYEE AND SECURE DATA

Step Why do this

  1. Save the contents of a former employee's mailbox This is useful for the person who is going to take over the employee's work, or if there is litigation.
  2. Forward a former employee's email to another employee or convert to a shared mailbox This lets you keep the former employee's email address active. If you have customers or partners still
Jayce
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  • Is there any update on this thread? If the issue has been resolved, please mark the helpful replies as answers – Jayce Feb 24 '21 at 06:53