Question of email security on these days is even more important since the beginning to use it for sending sensitive information. The cause of this is possibility to fake an email sender’s name.
In case of Sarah Palin, her email was hacked and all information was posted as a screen-shot. Anyone of us can be in her place, even if you’re not governor. Freedom of information laws demands, that messages from government email accounts should be declared in publicity. Some public figures use such e-mail giants like Yahoo or even Gmail to keep information from public eyes.
Public officials should bypass using public email addresses, even if they use absolutely anonymous names. System administrators see the content of mailboxes and easily can grab it in transmission because the information is owned by commercial email sites.
You should not be using commercial channels for private information transferring.
The level of risk will be lesser if user chooses email systems that offer strong encryption and authentication. The most powerful way to secure information is a strong authentication to avoid exposure of email content.