IPV6 is currently in its infancy, and as such has not yet been completely and fully certified for support with Enterprise Vault. IPV6 has been known to cause issues particularly around Outlook Web Access (OWA) and Enterprise Vault. See the Related Articles for further information. Although the Deployment Scanner utility does perform a check for whether IPV6 is enabled, this doesn't mean that IPV6 is expected to be enabled. For the time being it would be safer to disable IPV6 for any Enterprise Vault server and any server acting as an archiving target. Please consult the product documentation for the relevant operating system for instructions on how to do this.