Create a Shared Mailbox from an Existing Synced User Account

Connect to Exchange Online with Remote PowerShell

  1. Click Start


  2. Click Administrative Tools


  3. Right Click Windows PowerShell Modules and Run as administrator


  4. Set the Execution Policy on the local computer
    1. Set-ExecutionPolicy -ExecutionPolicy RemoteSigned
    2. Press “Y” for yes when/if prompted


  5. Specify remote credentials through a variable
    1. $cred=Get-Credential
    2. Enter Global Admin Account
    3. Enter password


  6. Set a session variable and connect to Exchange Online, enter command
    1. $s =New-PSSession -ConfigurationName Microsoft.Exchange -ConnectionUri -Credential $cred -Authentication Basic –AllowRedirection


  7. Import the session with the variable set in previous step.
    1. $importresults =Import-PSSession $s


Setup Shared Mailbox

  1. Convert the existing Synced user to a Shared Mailbox
    1. Get-Mailbox -identity
      | set-mailbox -type “Shared”


  2. Set the quota for Shared Mailboxes
    1. Set-Mailbox -ProhibitSendReceiveQuota 5GB -ProhibitSendQuota 4.75GB -IssueWarningQuota 4.5GB


  3. Setup the Security Group


  4. Create a security group for the users who need access to the shared mailbox
    1. Open Exchange Control Panel
    2. Select My Organization > Users & Groups > Distribution Groups > New.
    3. Specify a display name (Example: GDP_dg) (Descriptive Name and DG for Distribution Group)
    4. Specify an Alias (GDP_dg)
    5. Specify an e-mail address. (
    6. Select the Make this group a security group check box.


Note After you create a security group, the membership is closed. When membership is closed, only group owners can add members to the security group, or owners have to approve requests to join the group. Additionally, only group owners can remove members from the security group.

  1. In the Ownership section, click Add to add an owner, if necessary.


  2. In the Membership section, click Add.


  3. In the Select Members page, select the users you want to add.


  4. Click OK.


  5. On the New Group page, click Save.


Assign Permissions (PowerShell connected to Office 365)

  1. Assign the security group the FullAccess permission to access the shared mailbox
    1. Add-MailboxPermission -User SecurityDistributionGroup -AccessRights FullAccess


  2. Assign the security group the SendAs permission to the shared mailbox
    1. Add-RecipientPermission -Trustee SecurityDistributionGroup -AccessRights SendAs


  3. Hide the Distribution Security Group from the Global Address List
    1. Open Exchange Control Panel
    2. Select My Organization > Users & Groups > Distribution Groups
    3. Select the group that you created in the above step
    4. Select Hide this group from the shared address book
    5. Click Save


Once the above steps are completed, you can open the Microsoft Online Portal, click Users, Select the User account for the Shared Mailbox and remove the license.