I'm having a strange issue with office 365 (latest) & Exchange 2016.
I've shared one users mailbox (User A) with another (User B) and visa versa. Both have Full access to each other's mailboxes.
When I open outlook on User B, automapping does not occur. If I go to Account settings, and manually add User A's mailbox - it appears below user B's mailbox - but the contents is exactly the same as that of user B's mailbox. Also - if I close Outllook and re-open it - it's gone, but still there under account settings.