I'm just thinking about options for email-based services. I'm assuming a normal corporate user would be able to access them. For sensitive applications - eg bank account, purchasing with a credit card etc - you'd like mails to be secure. It looks like Outlook allows security features but I suspect you would not normally be able to activate these options at work. Can you think of other similar software approaches that would work in a corporate environment ie you might not have admin rights and you have no special rights to the mail server?