As part of our migration from 2010 to 2013, we have just moved our public folders across to 2013. In doing this, some, but not all, Outlook Clients are asking for credentials to access the public folders everytime Outlook opens. Looking at the connection status in outlook while the prompt is open, it is already saying the connection is established. The client still says connected even when cancelling the prompt. This is driving users mad. Our exchange is external to the LAN domain, and have checked the OutlookAnywhere External Authentication method are set to NTLM. I have created new outlook profiles, cleared windows credential manager on clients, used domain\username as well as UPN, and checked the autodiscover address is correct, all to no avail. The affected clients already have http://support.microsoft.com/kb/2817371 applied to them.
I am really not sure where to go next. Any help is much appreciated.