Hi,
I have created a shared mailbox in Office 365 administration. Within the settings I have gone to Mailbox Delegation and added users to the Full Access as well as the Send As permissions.
Within Outlook, if a user tries to Send As - from the email address associated with the shared resource, they get a bounce back.
However, if they reply to an email from the shared mailbox, it populates the FROM box with the shared email address and the user is then able to sand as this shared email address.
Anybody know how to diagnose this one?