Shared Mailboxes with no Delegates

I have seen several scripts to list shared mailboxes and who has been delegated access to them. Either full access or send as or send on behalf of. My issue is a little different.

I have over 1100 shared mailboxes. Most of these are term’d employees where our policy is to convert every E3 (Full office License) user to a shared mailbox, however we do not delegate any access to managers or others unless they specifically ask for access.

Is it possible? and if so how would I pull a list of every shared mailbox that does not have any delegates assigned to them, and has not been accessed in a period of time, so I can get permission to start removing these from O365.