When you assign a retention policy to the mailbox "{0}", any managed folder policy currently assigned to this mailbox will ...

When you assign a retention policy to the mailbox "{0}", any managed folder policy currently assigned to this mailbox will be cleared. In addition, client computers running Outlook 2007 or earlier versions don't have all available client features and aren't supported. You can use the Set-CASMailbox cmdlet to enable client version blocking. Are you sure you want to assign a retention policy to this mailbox?