Besides the very comprehensive explanation of the whole topic TeleTrusT also points out that most companies have too little security in place when it comes to daily e-mail use. They compare not encrypting e-mails to letting someone unknown deliver a postcard for you. With around 60% of the companies using transport encryption but almost none at all actually encrypting the e-mail itself they see an urgent need for action.
Most of the time companies as well as the daily users are not aware of the lack of security when sending a regular mail and by this risk at least privacy breaches, data loss or even manipulation. With its brochure TeleTrusT helps clarifying the whole topic and by this hopefully gets companies to be more aware of what they can do to protect their own as well as their customers' and partners' data.
Go here for the German version of the press release and the brochure.