Do deleted emails live on?
The Electronic Frontier Foundation (EFF), a nonprofit advocacy group, recommends that you configure your email client to delete emails from your service provider’s server once you download them. Of course, if you’re using a Web browser to access the email directly on their server, those emails will be there until you delete them — and even then they may be stored temporarily in a “deleted mail” folder for a specified number of days. In most cases, users can change that number of days.
The EFF also suggests that the best protection is to carefully consider what you want to commit to any form of communication before doing so, since it’s virtually impossible to ensure security.