When I have a shared mailbox and assign an owner to it, users will see the mailbox automatically in the Outlook client. As an owner they can add the mailbox to a new (clean) profile. We want to use the least privilege principle, that's why we don't want to give owner rights to everyone who needs access, that is just too much.
But we are facing problems with delegating access with minimum permissions on Exchange Online Shared mailboxes.
With PowerShell I gave permissions to the root of the mailbox and the Inbox folder with: Add-MailboxFolderPermission -Identity "<testmailbox>:\" -AccessRights FolderVisible-User <EmailofDelegate> Add-MailboxFolderPermission -Identity ""<testmailbox>:\inbox" -AccessRights reviewer -User <EmailofDelegate>
When I'm in my own profile I can open the other folder in Outlook with: File - Open & Export - Other User's folder without any problem.
But when the user tries to open the mailbox as a new profile they receive the error as shown in the picture:
Also when I try to open the mailbox in Outlook Web app it gives me an error: