Do not read your emails on an open network if you're that paranoid about evesdroppers. Wait till you get home and use a LAN cable.
If you have no choice and you have to use an open connection, then use certificates to encrypt the emails that you send to others (and let them encrypt their emails to you). I've never done that, so I'm afraid I cannot help you any further with this.
As far as I know, a VPN is only used to communicate between 2 computers. As soon as you're fetching information from the outside, there's no encryption. But you can use a VPN to set up a connection to your computer at home and check your Emails from there.