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Roger Roger 6,041 Reputation points
2024-09-07T22:09:31.1633333+00:00

Hi All,

I am using an Exchange 2016 hybrid environment. We create shared mailboxes on-premises and migrate them to Exchange Online, or create remote shared mailboxes from on-premises. Let's say my shared mailbox is [email protected]. I have a few external users (i.e user type is guest), and I want to provide them with delegated access to this shared mailbox. I have created a mail-enabled security group and added these guest users. Is it possible to provide delegated access/calendar access to the shared mailbox for these guest users?

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Accepted answer
  1. Xintao Qiao-MSFT 3,205 Reputation points Microsoft Vendor
    2024-09-09T02:50:21.37+00:00

    Hi, @Roger Roger

    In Exchange 2016 hybrid environment, providing delegated or calendar access to shared mailboxes for guest users can be somewhat complex because of certain limitations and constraints.

    First, delegated permissions across environments are migrated via DirSync, but delegated access may not work properly when principals and delegates are distributed across on-premises and online environments. This means that if the shared mailbox is in Exchange Online and the guest user is on-premises, or vice versa, delegated access won't work as expected.

    In addition, mailbox permissions, such as Send As and full access, are migrated when a mailbox is moved through the Mailbox Replication Service. However, the mailbox permissions for referenced distribution lists and mail-enabled users are not retained and must be manually re-added using cmdlets such as Add-RecipientPermission and Add-MailboxPermission.

    If you've created a mail-enabled security group and added guest users, you need to make sure that these guest users have the appropriate licenses and are properly configured in Azure AD, make sure that mail is enabled, and sync between on-premises and Azure AD, then you can try the following commands.

    If you want to assign full access:

    Add-MailboxPermission -Identity [email protected] -User [email protected] -AccessRights FullAccess -InheritanceType all

    If you want to assign calendar access:

    Add-MailboxFolderPermission -Identity [email protected]：\Calendar -User [email protected] -AccessRights Editor

    More information can be found Add-MailboxFolderPermission (ExchangePowerShell) | Microsoft Learn

    If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".

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  1. Amit Singh 4,896 Reputation points
    2024-09-09T06:56:18.1366667+00:00

    If you want to give access of shared mailboxes to guest users. You can do this by running the command in Powershell.

    For Full Access Permission- Add-MailboxPermission -Identity "[email protected]" -User "YourSecurityGroup" -AccessRights FullAccess

    By running this command, it allows members of the group to fully access the mailbox.

    For Calendar Access permission- Add-MailboxFolderPermission -Identity "[email protected]:\Calendar" -User "YourSecurityGroup" -AccessRights Editor

    Also check guest users have Microsoft accounts to properly access the mailbox.

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  2. Roger Roger 6,041 Reputation points
    2024-09-12T22:40:08.5+00:00

    Do i need to assign any license to guest users? will exchange online plan1 license work?

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