Forum Discussion
Why does a user have access to a Shared Mailbox
The 'usual way' of giving someone access to a Shared Mailbox in Office365, is to add them to the list of 'Members'. Now, I have a user who has access to a shared mailbox, which is fine, but I can...
The most likely way is your last hunch of it being logged directly into, since you can still technically log into a shared mailbox as long as the account is not disabled.
He might also have folder-level access. Simply looking into how the account is added in Outlook should give you the answer.