If I send a HTML email to a group which contains an iframe, an img tag, and an input field of type "image", all referencing a remote URL, the process of viewing

If I send a HTML email to a group which contains an iframe, an img tag, and an input field of type "image", all referencing a remote URL, the process of viewing the email in the posterous interface automatically causes the browser to fetch each of those resources. This is a privacy leak. You should remove references to these remote resources when displaying a message in the posterous web interface. You should then provide an option to "Load Remote Images". Much like most email clients do.