DNS pre-fetching is a great way for spammers to determine whether or not an email has been read when the recipient is using webmail with a browser which support

DNS pre-fetching is a great way for spammers to determine whether or not an email has been read when the recipient is using webmail with a browser which supports it. Although, I believe DNS pre-fetching is disabled over https by default on all current browsers which support it. EDIT: This is one of the things that a website I developed tests for: https://emailprivacytester.com/ https://emailprivacytester.com/