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How can we improve the tenant admin features O365?

Support conversion to shared mailbox for synced users

Currently a mailbox for a synced user can be converted to shared in EAC. This results in a corrupted mailbox object and an Azure AD object that still requires a license. See Customers need to move the mailbox to on-premises Exchange, convert it to shared and then move the mailbox back to Exchange Online. This process can be cumbersome and even worse, if customer is not aware of this issue the shared mailbox will be removed after the grace period expires.

It should be supported to convert a mailbox to shared for a synced user in Exchange Online, or customers should be prevented from doing this and ending up in a bad situation by removing the 'Convert to shared' option in EAC for synced users.

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Jetze Mellema shared this idea  ·   ·  Flag idea as inappropriate…  ·  Admin →


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  • Anonymous commented  ·   ·  Flag as inappropriate

    Hi Guys, not true anymore for a Hybrid environment.

    Move your user mailboxes and feel free to convert them afterwards in EXO
    However, we still have a limitation of writeback attributes in the sync.

    So for the corresponding onprem account change this attributes to this values,

    msExchRemoteRecipientType: 100
    msExchRecipientDisplayType: -2147483642
    msExchRecipientTypeDetails: 34359738368

    This will make the shared mailbox shown under shared mailboxes in onprem Exchange Admin Center.

    All confirmed by Microsoft Support.

  • Mike Walker commented  ·   ·  Flag as inappropriate

    Does the problem still exist if you can put a license on the converted mailbox? We are running short of E3 licenses but have a bunch of users being offboarded, so I am converting them to Shared. We do have spare F1 licenses at the moment, so I am replacing the licenses at the same time (and we grant FullAccess or Forwarding to a delegate as needed).

    Shared Mailboxes are not supposed to need licenses, but if I assign one anyway - does that prevent the account from being converted back to a regular mailbox?

  • Nilis commented  ·   ·  Flag as inappropriate

    Microsoft is still advising to onboard mailbox and convert and sync back....
    Why is this still not solved. Looks fairly easy to sync the required attributes back to Exchange.

  • Daniel Mueller commented  ·   ·  Flag as inappropriate

    There is a quick fix: Just assign a license to the synced user with the shared mailbox, then remove the license again and it will change back to normal. Or assign a license before you convert the mailbox to shared an remove the license.
    Still, this issue should not appear, 3 votes.

  • Phil Williams commented  ·   ·  Flag as inappropriate

    I have a variation on this issue that is driving me mad!

    Basic Hybrid setup not full

    I create a brand new Shared mailbox in O365 and configure it. Everything is fine.

    Then when the next sync hits a new 'in cloud' unlicensed user appears in the Active users view with a name that matches my new shared mailbox.

    Is this expected and OK or are my shared mailboxes going to vanish after the grace period?

    account does not exist ii AD and never has... so what's happening here ?

  • Marco Moretti commented  ·   ·  Flag as inappropriate

    We have the same problem. In Exchange Online (Hybrid Deployment) we need to convert a shared mailbox to regular mailbox (with license) and viceversa but the only solution suggested is offboarding the mailbox, convert onpremise and re-onboarding.
    For us in an enterprise environment, this is not acceptable because some mailbox are large 15-20 Gb and this conversion should be done several times a year.

  • Timo Lindenschmid commented  ·   ·  Flag as inappropriate

    You can use powershell/ADSI to modify the recipient display type AD attribute on prem from shared to user and vice versa, after sync the mailbox will be converted accordingly automatically by Exchange.

  • Drew Lanclos commented  ·   ·  Flag as inappropriate

    This only applies to hybrid deployments. It works fine if you're not hybrid.

    The shared mailbox is still unfortunately tied to a dirsync'd user and so you can't disable dirsync for that user or the mailbox goes bye-bye...

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