Outlook 2010 prompt for credential when connecting to Exchange 2013 mailbox

I have 4 server Exchange 2010 with DAG and one server Exchange 2013, i've migrated some mailbox to the new 2013 server.

I'm having a problem with some Outlook 2010 that sometimes (not always) requires credential to connect to mailbox in a server Exchange 2013, but only when Cache mode is enabled.

The client ask for credential and dont connect to mailbox until I change in online mode.In Online Mode, everything works fine.

I don't have Public Folders, so the check box Download Public Folder is not selected and the authentication mode is "Negotiate".

Thanks in advance.

Elisa