Hello,
We are running Exchange 2013 (Cumulative Update 23 (CU23)).
CU23 was recently installed, along with the Zero Day Patch.
The following day, we have been receiving reports that all users are being prompted for credentials frequently throughout the day.
The message is as follows:

PF-Mailbox is the name of the Public Folder Mailbox.
Action taken so far with no success.
Recreated Outlook profile for a few users.
Switch between Online/Cached mode.
I don't see any errors on the server.
Any suggestions?
Thanks in advance.
Regards,
Rudy