Open PowerShell as Administrator
Login with an account that has Administrative access to your Office365 tenant
If the user who you want to grant access to already has FullAccess permission, or has been delegated FullAccess permission using the Microsoft 365 Exchange dashboard run this command below before you proceed.
Remove-MailboxPermission -Identity "email@example.com" -User "Jdoe@kbtechpro.com" -AccessRights FullAccess -InheritanceType All
This example will remove ‘FullAccess’ permission from user Jdoe on mailbox ‘firstname.lastname@example.org‘.
Use the following command to grant Readaccess to the mailbox for the specified user.
Add-MailboxPermission -Identity "email@example.com" -User Jdoe@kbtechpro.com -AccessRights ReadPermission
Grant permissions to the top information store.
Add-MailboxFolderPermission -Identity firstname.lastname@example.org:\ -User Jdoe@kbtechpro.com -AccessRights Reviewer
This example grants the user ‘Jdoe’ Reviwer permissions to the shared mailbox ‘email@example.com’ top level information store.
Grant Access to the Inbox & Outbox Folders
Add-MailboxFolderPermission -Identity firstname.lastname@example.org:\Inbox -User Jdoe@kbtechpro.com -AccessRights Reviewer
Add-MailboxFolderPermission -Identity email@example.com:\Outbox -User Jdoe@kbtechpro.com -AccessRights Reviewer
The two commands above grants Read-Only access to the outbox and Inbox folders to user Jdoe.
Be sure to grant access to inbox and outbox. In our experience grant access only to inbox resulted in an error when attempting to add the mailbox.
The next step is to open Microsoft Outlook and add the shared mailbox. Unfortunately, the permission level ‘ReadAccess’ does not support automapping. This is why it needs to be manually added to the outlook profile.
The AutoMapping parameter includes or excludes the mailbox from the auto-mapping feature in Microsoft Outlook. Auto-mapping uses Autodiscover to automatically add mailboxes to a user’s Outlook profile if the user has Full Access permission to the mailbox.
-Source: Microsoft Learn ‘https://learn.microsoft.com/en-us/powershell/module/exchange/add-mailboxpermission?view=exchange-ps‘
Open Outlook and navigate to File > Account Settings > Select Account Settings from the drop down list.
The mailbox should now be visible to the user in outlook.
Be sure the expand the mailbox folders by clicking the arrow beside the mailbox name.