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Summary: This content highlights Office 365’s mailbox delegation to manage email overload in business. It explains permissions, offers step-by-step instructions, and suggests the Kernel Office 365 Migration tool for efficient data migration. Technical skills may be necessary for some tasks.

In the realm of business, certain email accounts receive a higher volume of messages compared to others, leading to challenges in promptly addressing each communication. To address this issue, Office 365 offers a solution: mailbox delegation. This feature allows administrators to grant control of a mailbox to another user, enabling them to respond to emails on behalf of the original account holder. The administrator possesses the capability to manage permissions for the designated mailbox, including granting read and write access to the delegated user. This delegation of permissions empowers users to perform various actions, including:

  • Read email from another mailbox.
  • Send email from another mailbox.
  • Send email on behalf of another mailbox.

Note – it takes up to 60 minutes for the changed permissions levels to propagate completely.

You can assign these permissions to other user mailboxes using either the Microsoft 365 admin center or Exchange Online PowerShell cmdlets.

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Let us know what these mailbox permissions are

  • Read and Manage: This permission grants the assigned user mailbox(es) the ability to both read and manage emails within the user mailbox to which the permission has been granted.
  • Send as: This permission allows the assigned user mailbox(es) to send emails from another user’s mailbox on which permission is assigned.
  • Send on behalf: This permission allows the assigned user mailbox(es) to send email on behalf of the mailbox on which permission is assigned.
Assigning Permissions to Another User Mailboxes via Microsoft 365 Admin Center

Now that we have discussed the permissions a user mailbox can assign to other user mailboxes, let’s outline the procedure for assigning these permissions using the Microsoft 365 Admin Center interface. Here are the steps:

  1. Log in to your Microsoft 365 account and click Admin.
  2. Then, go to Users>Active Users. Double-click on any desired user and then under Mail Settings section, click Edit option against Mailbox permissions.
    Mailbox permissions
  3. A new page Edit mailbox permissions will get open. Here, to set permissions for user mailboxes, click Edit against Read and manage feature.
    Read and manage feature
  4. Click +Add permissions to add the user mailboxes whom you want to assign this permission.
    Click +Add permissions
  5. Select the desired user mailboxes from the list and then click Save.
    Select the desired user mailboxes
  6. Thus, user mailboxes are assigned permissions.
    user mailboxes
  7. Similarly, you can assign Send as and Send on behalf permissions to other user mailboxes.
Assigning Permissions to User Mailboxes through Exchange Admin Center

You can also set permissions for the selected user mailboxes via the Exchange Admin Center.
Now, head on to the steps through which you can assign these permissions.

  1. Open your Microsoft 365 account with the login credentials.
  2. Click Admin and then open EAC by navigating to Admin centers>Exchange.
    Open your Microsoft 365 account
  3. In EAC, click recipients and then select mailboxes option. Then, select the desired mailbox and click the Edit icon.
    Note: You can select multiple mailboxes and under Bulk Edit on the leftmost pane, click More options and choose Mailbox Delegation option to assign the permissions to mailboxes simultaneously.
    choose Mailbox Delegation option
  4. Now, select mailbox delegation option from the left pane and then click + icon under Send As to select the user mailboxes and assign them this permission.
    select the user mailboxes
  5. Select the user mailboxes to which you want to assign this mailbox permission, click add -> and finally click OK to add them.
    click OK to add
  6. Likewise, you can assign other mailbox permissions like Send on behalf and Full access.

Another way to assign these mailbox permissions to the Microsoft 365 user mailboxes is the use of PowerShell cmdlet. It is quite a technical procedure and requires prior knowledge of using and running cmdlets in the Exchange PowerShell.

To run the PowerShell commands for assigning the permissions, you need to connect Windows PowerShell to Exchange Online first.

How to connect to Exchange Online PowerShell?

Follow these instructions to connect to the Exchange Online PowerShell.

  1. First, run the Windows PowerShell as administrator (right-click on the application icon and choose Run as administrator option).
  2. Run this command.
    $session = New-PSSession -ConfigurationName Microsoft.Exchange -ConnectionUri “” -Credential $cred -Authentication Basic -AllowRedirection
  3. Enter the Microsoft 365 global account credentials in the opened window and click on OK.
  4. Now, run this final command to connect Exchange Online to PowerShell.
    Import-PSSession $session
Assign Mailbox Permissions with PowerShell cmdlets

Now assign the permissions to the selected mailbox with the execution of following cmdlets in the Exchange Online PowerShell.

  1. To assign Send As permission to a user mailbox, run this command
    Add-RecipientPermission <Identity> -AccessRights SendAs -Trustee <Identity>
  2. Assign Send on Behalf permission to a user mailbox with this command
    Set-Mailbox <Identity> -GrantSendOnBehalfTo <Identity>
  3. Assign Full Access permission to single user mailbox with this cmdlet.
    Add-MailboxPermission <Identity> -User <Identity> -AccessRights FullAccess -InheritanceType All

    Note: In the above cmdlets, provide the desired value in place of as per the requirement.

We’ve covered these manual techniques for assigning mailbox permissions to Microsoft 365 user mailboxes. While users with technical expertise may find these methods straightforward, those less familiar with technical procedures, especially when dealing with PowerShell commands, might encounter difficulties.

If you are interested in data migration between Microsoft 365 tenants, perform bulk mailbox migration to Microsoft 365 or any other Microsoft 365 migration, we offer the perfect solution from our end. The Kernel Office 365 Migration tool is designed specifically to help its users in attaining a smooth, simple and efficient cloud migration.


Office 365 administrators can allocate permissions to different user mailboxes through both the Office 365 Admin Center and Exchange Management Shell cmdlets. Typically, these permissions are assigned to mailboxes to facilitate data-related tasks, and when migrating mailboxes, it becomes important to migrate these permissions as well.

Kernel Office 365 migration software helps you to perform Office 365 tenant to tenant migration along with their permissions and complete features. In a new destination, the mailboxes will find them comfortable and usable instantly.

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