When assigning a managed folder mailbox policy with managed custom folders to the mailbox "{0}", Outlook clients older than ...

When assigning a managed folder mailbox policy with managed custom folders to the mailbox "{0}", Outlook clients older than Outlook 2007 do not have all available client features and clients older than Outlook 2003 SP2 are not supported. You may use the "Set-CASMailbox" task to enable client version blocking. Are you sure you want to assign a managed folder mailbox policy to this mailbox?