Working with public folders with Outlook 2013

Hello!

I'm running Exchange 2013 Ent + Outlook 2013 and is testing public folder functionality. I logged into Outlook as Administrator and also have user1's and user2's mailboxes connected as mailboxes with delegated access. When I create a post in a first-level public folder it is posted as coming from user1, not from Administrator:

When I create a post in the second-level public folder it is posted as from Administrator - why???

Thank you in advance,

Michael