Office 365 mailbox migration

How would I go about giving a new user created in Office 365, the mailbox of an old user that left the company? In a in-house Exchage server you create the new user and attach the old mailbox. I'm not sure how to do that in Office 365.

Thank you
Alan DalaITAsked:
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Vasil Michev (MVP)Commented:
In theory, not possible with Office 365. In practice, you can abuse the dirsync feature to achieve this. Here are the steps, use at your own risk:

1) Remove the account associated with the mailbox in your AD
2) Wait for (or force) dirsync to reflect the changes - the resulting user will be moved to the Recycle bin in WAAD
3) Recover the user in WAAD, DO NOT recover him in your local AD. This will provision the user object as disconnector in the metaverse
4) Force dirsync few times to make sure the recovered object will not be removed again (happens occasionally)
5) Use either the soft matching or the hard matching methods to link the recovered object to another object in your AD. If you are going with soft match, clear the ImmutableID first

If I get some free time today, I will put up a blog post with more detailed information on this.
Alan DalaITAuthor Commented:
What would be an easier and less dangerous way to do that? Should I just create a PST file and migrate it into the new account?

Vasil Michev (MVP)Commented:
Yup, this is a pretty safe option. Might be a bit slow however, so instead you can use the Search-Mailbox cmdlet to copy all the content to a new mailbox 'server-side':
Making Bulk Changes to Active Directory

Watch this video to see how easy it is to make mass changes to Active Directory from an external text file without using complicated scripts.

Gareth GudgerSolution ArchitectCommented:
If you wanted to keep the mailboxes separate, you could grant the new user FULL ACCESS rights over the old mailbox.
Alan DalaITAuthor Commented:
Thank you Gareth,

This might be the way to go if I had an extra Office 365 license. In order to create a new account in Office 365, we need to delete the old user...I don't think there is a way in Office 365 to access the mailbox of a deleted user...
Gareth GudgerSolution ArchitectCommented:
If the old mailbox is under 5GB you could convert it to a Shared Mailbox, which doesn't consume a license. Licenses follow the number of users, not the number of mailboxes.

Because that is what it is basically becoming - a non-user mailbox.
Alan DalaITAuthor Commented:

I did that but when I tried to remove the license, it gives me this warning about losing all the data which defeats the purpose of all this. If I change the mailbox into a 'Shared' one, I don't have the option to remove the license anymore, yet the license is not freed. Any help would be appreciated.

Thank you
Gareth GudgerSolution ArchitectCommented:
Found this thread. The Microsoft employee says you can uncheck this license. But they do recommend backing up the mailbox prior to trying this. You could export it mail to a PST first as a precaution.
Vasil Michev (MVP)Commented:
Yup, if you convert it to shared and keep the size under 10GB, you will not need a license. You can also look at the inactive mailboxes functionality (if you need to keep old content for legal reasons):

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Gareth GudgerSolution ArchitectCommented:
Ah. I forgot they raised the Shared Mailbox from 5 to 10GB.
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