In my posting last February, Prototyping Multilevel Mail, I discussed some techniques for implementing an email service to support labeled zones. It turns out that a company called BlueSpace Software has done just that. They have a very cool demo showing their label-aware email client running under Trusted Extensions using the Trusted Java Desktop System. The product is called BlueSpaced TransMail Trusted Edition. Here is a quote from their web page:
TransMail Trusted Edition tightly integrates with Solaris 10 Trusted Extentions to ensure appropriate content management between the different security zones, including data labelling so that the interface operates mutliple network sessions simultanteously.
I haven't had a chance to try it out, but I'm looking forward to doing so when it is available.