Configuring preferences and options in Outlook.com
Main Mailbox emails when flagged shows up at the right handside of the mailbox.
When the shared mailbox emails, when flagged, shows up as flagged just on the email, but doesnt show up on the right handside.
What happens when you try to flag a message?
Nothing.
This is a Microsoft Exchange shared mailbox? Flags are supported in shared mailboxes but you need Edit permissions.
Yes, Edit permissions where?